If someone says "hey, can you do this?" and I respond "yeah, later." I see that as just saying I'll do it. If they talk to me and say "this is important for reasons X,Y,Z, can I count on you(or something like that)" and I say "Yes, I will make sure it gets done in this fashion." I see the first as just kind of acknowledging that they spoke to me and trying to keep it in mind, but the second as actually me consciously agreeing to it. A promise could be more like my giving my word or swearing to it depending in the context. My view is my word means I am binding myself to an action and will see it done, but I could theoretically try to back out(by talking to them about it) if something else comes up or the circumstance changes. If I swear to something, I have to see it done, come hell or high water. I can come off as overdramatic about this sort of thing. This is because I am both religious and practice a code of honor, which heavily influences what I place value in.