Ascomycota or sac fungi make up about 75% of all known fungi species.
It is a very general category to describe a large number of organisms. Yeasts are some of the more well known Ascomycota species. More specifically, some common species include
Saccharomyces cervisiae (baker's yeast)
Penicillium chrysogenum (penicillin)
Morchella esculentum (morels)
Candid albicans (which causes diaper rash, and some other human rashes)
There are many species included in this class but these are a few of the more common.