A keystroke is the single pressing or clicking of a key on a computer's keyboard. Keystrokes per minute (KSPM) is a common measurement of typing speed in addition to words per minute (WPM). Some applications and websites also use keystrokes as event triggers.
Each keystroke on a keyboard sends a signal to the computer. This signal tells the computer which key the user pressed, how long they held it down, and whether it was pressed alone or with another key. Most keys on a keyboard will type a letter or symbol when clicked. Other keys, called modifier keys, do nothing when pressed on their own but trigger a keyboard shortcut when combined with another key. A computer's operating system receives the keystrokes, then either sends a command directly or passes the keystrokes to the application that currently has focus.
Certain types of software, called keyloggers, keep records of every keystroke a user makes on their computer. Some keyloggers have legitimate purposes, like assisting in software troubleshooting or product development feedback, but viruses and malware also often include keyloggers. These keyloggers monitor a computer user's activity secretly to steal passwords and other personal information, then report every keystroke to a remote computer.