Can someone please for the love of God explain this to me?

I’m very new to this genre of games. I have zero clue what I’m doing. I am still enjoying the game but I’m tired of constantly walking into traps and getting failed perception tests or whatever when I’m just walking. How do I not do this. Like do I have to do anything myself or is it just random that the characters will notice a trap. Do I need to be in stealth mode?