These are "adverbials of probability".
Adverbs of probability are used to show how sure we are about a situation or event.
definitely, certainly, clearly and obviously show that something is very likely to happen (very high probability)
- We will definitely be there tomorrow.
- She is certainly coming to the party.
- It is clearly going to be wonderful weather tomorrow.
- They are obviously late.
possibly, perhaps, probably, maybe show that something may or may not happen:
- I’ll probably go out tonight - more likely than not
- I'll maybe go out tonight. - less certain
perhaps and possibly show that something is less likely to happen (low probability)