Like the comment above mine, "I guess" is a way of agreeing to something, but not whole-heartedly. It's more like sort-of saying that you agree with something. Let us say you don't really like hamburgers, but your whole family does, and they suggest going to get hamburgers for dinner. They ask you if you want to get them, and, since you don't want to make a problem out of it, you respond with "I guess..." It doesn't mean no, but it doesn't mean yes, it's in the middle. "I bet" is a phrase that can be used to agree with a situation. Here's an example conversation: "I tripped and broke my ankle!" -"Really?" "Yeah, and it really hurt." -"Ouch, I bet" So "I bet" is kind of saying you agree and that something obviously happened, like how breaking your ankle would obviously hurt. It's pretty confusing and honestly, I don't typically use or hear lots of people saying "I bet" on an everyday basis, so if you don't completely understand its fine and there are many alternatives to the phrase. Nonetheless, I hope this helped!

They can mean the same, depending on context, but can have differences. For example, a guess has a certain element of randomness (i.e. I'm thinking of a number between 1 and 10 - can you guess which one it is?). If there is less randomness, it can be called an 'educated guess', where you eliminate obviously incorrect options and randomly select one of the remaining possibilities. Often, a bet concerns a gamble of some sort (i.e. I bet you $1 I can throw a 6 before you do). They can also be used as answers to a question or statement. 'I bet' will confirm the statement, whereas 'I guess' will be used to show uncertainty. For example, "The weather will be fine tomorrow - we could go to the beach!" "You bet!" (I agree - let's do it) or "I guess ..." (I'm not sure - we'll see) Hope that helps.