[SOLVED] Extremely trivial question

[Ventilaator]

This has been bothering me for some time, but sometimes when accidentally pressing some key, my cursor selection mode changes to always select a character upon click like this...



This is really frustrating, because whenever I need to type anything, the cursor selects a char forcing me to overwrite it.

I know it's a really trivial question, but can anyone tell, what is the key shortcut to change cursor selection mode (how cursor reacts when clicking on any random point)?

Thanks in advance,
Vent