ICDL Computer & Online Essentials (ICDL) key terms

The physical parts of a computer that you can see and touch, such as the screen, keyboard, processor, cables and printer. Hardware needs software to tell it what to do.

The programs and instructions that run on a computer. Software is not physical: it tells the hardware which tasks to carry out, from starting the machine to editing a photo.

The main software that starts when a computer is switched on. It manages the hardware, files and other programs, and provides the interface the user works with, such as Windows, macOS or Linux.

A program designed to help a user complete a particular task, such as writing a document, browsing the web or editing photographs. It runs on top of the operating system.

The chip inside a computer that carries out program instructions and performs calculations. Often called the processor, it strongly influences how quickly a computer responds and runs tasks.

Random access memory, the fast temporary workspace a computer uses for the programs and files currently open. Its contents are erased when the computer is switched off, unlike storage.

The place where files and programs are kept permanently, for example a hard disk, solid-state drive or USB stick. Data in storage remains available after the computer is turned off.

Any piece of hardware attached to a computer to add a function, such as a printer, scanner, mouse or webcam. Peripherals may be built in or connected externally by cable or wirelessly.

Hardware used to send data or commands into a computer, for example a keyboard, mouse, touchscreen, microphone or scanner. Without an input device the user could not control the machine.

Hardware that presents results from a computer to the user, such as a monitor, printer, projector or speaker. It turns processed data into something a person can see or hear.

A named unit of stored data on a computer, such as a document, photograph, song or program. Every file has a name and usually an extension showing what type it is.

A copy of files or data kept separately so the originals can be restored if they are lost, damaged or deleted by accident. Backups are often held on an external drive or in cloud storage.

Two or more computers or devices connected so they can share data, programs and resources such as printers or an internet connection. Networks may cover one room or the whole world.

The worldwide system of connected computers and servers that lets people share information and use services such as email, messaging and the web. It links millions of smaller networks together.

The collection of web pages and sites stored on servers around the world and viewed through a browser. The web is one service that runs on the internet, not the internet itself.

A company that sells access to the internet, for example through broadband, cable or mobile data. The provider connects a customer's home or device to the wider network.

A device that directs data between networks and usually shares one internet connection among several devices in a home or office. Many home routers also provide a Wi-Fi signal.

A technology that connects devices to a network without cables, using radio signals over short distances. A device must be within range of the router or access point to connect.

A program used to open, view and move between web pages, such as Chrome, Firefox, Safari or Edge. It requests pages from servers and displays them on the screen.

Uniform Resource Locator, the address of a page or file on the web, for example https://www.example.com/page. Typing a URL into a browser takes you directly to that location.

A website or service that finds pages matching the words you type, using an index of the web, and lists results in order of relevance. Common examples are Google and Bing.

To copy a file or data from a website or server onto your own device. The reverse process, sending a file from your device to a server, is called uploading.

A service for sending and receiving written messages and files over the internet. Each message is addressed to a recipient and waits in their mailbox until it is opened.

The unique identifier used to send email to a person or organisation, made up of a user name, the @ symbol and a domain, such as [email protected]. It must be typed exactly to arrive.

A file such as a document, photograph or spreadsheet sent along with an email message. Attachments may have size limits and should be opened with care when unexpected.

Two ways of copying extra people on an email. CC (carbon copy) shows every recipient's address to everyone; BCC (blind carbon copy) hides those addresses from other recipients.

The accepted rules of polite behaviour when communicating online, such as avoiding typing in capitals, staying on topic and respecting other people's time, privacy and opinions.

An online service where people create profiles, connect with others and share posts, photographs and messages. Examples include Facebook, Instagram and LinkedIn.

A form of online chat in which short messages are exchanged in real time through an app or website. Many services show whether a contact is currently online.

A live audio and video meeting held over the internet between people in different places, often with screen sharing. It requires a camera, a microphone and a reliable connection.

A secret string of characters used to prove your identity and protect an account or device. Strong passwords are long, hard to guess and not reused on other sites.

A security method that requires two different proofs of identity to sign in, such as a password plus a code sent to your phone. It makes a stolen password much less useful to an attacker.

A scam in which someone sends a fake message, email or link that pretends to be genuine, in order to trick you into revealing passwords, bank details or personal information.

Short for malicious software: programs designed to harm a computer, steal data, spy on the user or display unwanted adverts. Viruses, worms and ransomware are all types of malware.

A program that scans a computer for known malware, removes it where possible and blocks new threats as they appear. It must be updated regularly to recognise the latest dangers.

A security tool that monitors and filters network traffic, blocking unauthorised connections while allowing approved ones. It may be software on a device or a function built into a router.

Unwanted bulk email or messages, usually advertising or fraudulent, sent to large numbers of people at once. Spam filters move such messages into a separate folder automatically.

The process of scrambling data so that only someone with the correct key can read it. It protects information while it travels across networks and while it is stored on devices.

The trail of information you leave online through posts, searches, comments, sign-ups and purchases. It can be seen by others and may remain available for a very long time.