A little context would help to make this clearer. However, I think what you are referring to are situations like: Person 1: Hey, do you want to see this awesome exhibit with me at the museum?! Person 2: You bet! This 'you bet' is used to say something like 'Sure', 'absolutely', etc. It's an affirmative answer. and: "I bet you're happy that exams are finished for the school year." This 'I bet' is used to show an assumption, similar to how we might say 'I think...' or 'I imagine...' You can also use 'I bet' to show a prediction that something will happen. "I bet she'll go to the party tonight since her friends are all going." I hope that helps! :)

I would use you bet in a very simple way of agreeing with someone or emphasising what they say. I would tend to use 'I bet' when I am making a bit of a prediction: "I bet it will rain tomorrow" "I bet Sally will be late for the meeting".

'You bet' can also be used as an informal 'you're welcome'

"you bet" is when you are agreeing with the other person. "I bet" is when you are guessing about something.