What Does OK Mean?

 Sometimes it just means everything is OK.

In my travels around here and there and including in Europe and Israel I have noticed that there are a few Englishisms that are used everywhere.  One of them is OK.  A couple others are hi and bye.

I wondered then what do you mean when you say OK?  Does it mean I agree you are right, I will do as you say?

Or does it just mean I hear you, OK?

It might also mean I'm done now, leave me alone!

Sometimes it means Here Goes!

In similar fashion, I wonder about upticks.  I often use it to mean I saw that.  But sometimes to mean I think that's great.  Inconsistent. 

What say you?

BTW, Shabbat Shalom!