two kinds of yeast

I was just wondering what happens when you use 2 kinds of yeast weather it be 2 different wyeast or a dry and a liquid or two kinds of dry yeast?

It works. But my understanding is that one strain will eventually out compete the other. Part of the fun, I think, is toying with the timing, for instance, starting with one and then adding another more attenuative strain to finish things up. Actually, I'm thinking about making a wheat wine today that I'll first pitch on a CA ale cake, shooting for clean flavors, and then let a Franco-Belgian strain finish things off to get to a super-dry finish.

Oh, so it will change flavors, like if you use an ale yeast, then another that is more malty like one for a bock or Belgian

The flavors given off by the individual strains won't change but you will have flavors contributed by both strains.

Most of the flavor development happens in the first few days, so if you were to use two strains at different times, then the first one will impart most of the flavor characteristics. The only reason I can see to add another strain would be to lower the FG if the first strain stalls out. Hope this helps.

So it wouldnt matter if the yeast was dry or liquid and a combo of both

If I'm looking for two different yeast characteristics in the same beer, I'll ferment 10 gallons in two 5 gallon carboys using two different strains and then blend them when bottling.

It will matter depending on which flavor profile you are aiming for. What I have read is that the initial yeast pitched will theoretically give off more flavor than the second. if you are added them at different times. I have read this is the recommended procedure as you will have a little more control of the result. Without a lab and testing the two yeasts after mixing it is hard to say which will over-power the other.
It is also suggested that you use the less floculant of the two yeasts FIRST... Then after ~2 days of fermentation pitching the second. So two things to consider, which flavor profile (this would be my main concern) and which is less floculant...
Another thought is to get yourself several gallon jugs and airlocks to try one gallon batches and different blending schedules...Just remember to take good notes. If I had a nickel for every time my neighbors called me a mad scientist!