Selenium IDE uses 'Selenese' commands, which are categorized into three types: Actions (do something like click/type), Accessors (store a value for later use), and Assertions (verify a condition). It is primarily used for quick bug reproduction, prototyping, and learning Selenium basics. IDE records user interactions and generates Selenese scripts, making it ideal for beginners.
IDE is like recording a video of yourself using the app. You click, type, and verify things happen as expected. Selenese is the script of what you did, which can be played back anytime.
If Selenium IDE is so easy to use (Record & Playback), why do we spend time writing complex WebDriver code?