Regarding computer security, what is a keylogger?

-Ive been reading questions on here in Security and that word comes up a lot. By context Im guessing its got something to do with bootup. Is that right?A keylogger is something which records the keys you press. It's often used by hackers to get passwords etc.

Not something you want.No. A keylogger is software that you install on someone else's computer (or on a shared computer), that is not detectable by regular processes (so it's stealthy) and that will email you daily report of all keystrokes on that computer. So you can read other people's emails, chats, URL's, passwords, etc.
Keyloggers often 'install' before the OS (Windows for instance) gets 'booted' (running).

That means every key you touch is copied to a hidden file, and at whatever time it's set for: sends those files to a 'mothership' for further analysis (by bots usually).

They can also take 'screenshots' and have pixel location aspects, which show even more of what you're doing, so 'on-screen' keyboards (mouse letter selection) are a moot tactic against them.
A key logger is a root kit/malware that affects your PC and its mostly starts a system startup,For example if you login to mail.yahoo.com your username and password will be saved which can be seen by a hacker.To prevent such type of keyloggers antivirus cant help you need a software called Key-scrambler get it here- http://www.qfxsoftware.com/



Hope it helped.
A keylogger is just like a hidden camera in a room, which records every activity, regarding computer it is a kind of software which records the data of every single button pressed.
A keylogger is used to monitor you're keystrokes by an attacker when you enter passwords etc.