Intellij - what is this strange selection, and how do I turn it off?

Question

See the screenshot below to see what I mean. Basically, Intellij only highlights the box I draw with the cursor, but leaves the rest of the editor untouched. I have no idea why it happens, and the only way to resolve it for now is to close and reopen the editor. I have observed the same behavior on a Linux box and a MacBook, both when editing Java and PHP files, so I am not sure it's a bug.

The desired behaviour is standard row selection, i.e. highlight all rows which I drag the cursor over.

Answer 1

I think you have enabled 'column selection'.

Option can be toggled via these methods:

Menu Bar -> Edit -> Column selection mode

Document Body -> Right Click -> Column selection mode

Keyboard Shortcut -> ALT + SHIFT + INSERT