what are proton donors? why alcohols, alkynes are called so?

Proton donars are nothing but acids. According to Bronsted concept proton donars are acids. Alcohols and alkynes have H, which is donated as H⁺, that is why they are called proton donars and they have acidic properties.
R-O-H ---->  R-O^- + H⁺
R-C Ξ​ C - H  ----> R-C​Ξ​ C^-  + H⁺