You use it in different situations to indicate several emotions or responses : - It is the word everyone uses when someone just told you something and you literally can't come up with anything else to respond with. So you just say " I see " , sort of filling the gap of not responding at all :) - When you hear something really nasty or something you just could have gone without hearing you commonly use the words "I see" . So here you say that instead of being rude . - A conversational response which indicates a level of understanding without necessarily indicating agreement with the statement. It essentially means "I acknowledge and understand what you are saying". ( Lupin's explanation ) - Also used when you have no idea what the other person has just said but definitely do NOT want them to clarify. " We were at the MFS yesterday and Alex was there " " I see " ( responding when you don't know what MFS is or who Alex is ) -The new Lol. Used when the user is too lazy, bored, lazy to give a proper reply to whatever you just said.It is used in real life and on instant messengers and games and more.

"I see" is pretty similar to "I understand". It comes from the phrase "I see what you mean" which just means "I Understand" I can't think of any situations where it would be rude, it's just a simpler way tell someone you understand. If someone explains something to you, maybe instructions for something and you understand everything you can just use "I see what you mean" or " I see"

I seeは(そうか/そっか/そうですか)と同じ意味です。使い方も同じです。全然失礼ではないと思います。 だけど、もっと丁寧な場合は、I seeより、もっとちゃんとした答えを出した方がいいと思います。