How long does the effect of laser hair removal last?

I get self-conscious about my underarm hair every summer.
I don't usually wear sleeveless tops, but even when I wear short sleeves, I sometimes get self-conscious about it.
I have never had laser hair removal at a dermatology clinic before. However, lately, I have become very interested because it seems like a good treatment option.
Back in the day, I used to just quickly shave it off with an eyebrow razor at home lol;;;
It feels like my hair grows back a bit quickly, so I'm wondering how long the effects last if I get laser hair removal.

I'm curious about the treatment time, and basically, I have a lot of questions about laser hair removal. I wonder if it will be painful... I'm also curious if there are various treatment methods. Is it possible to shower and do things like that immediately after the procedure? Or do I need to apply some kind of ointment for about a day? Since I have absolutely no information about laser hair removal, I'm worried about a lot of things.