The name "Yoshi" is both a collective and proper noun. "Yoshi," in the collective sense, refers to a species of intelligent dinosaurs that inhabit several islands scattered around the Mushroom World. Yoshis come in a variety of different colors, with each color displaying unique characteristics and behavior.

Yoshi, in the proper sense, refers to the Green Yoshi that is Mario's best friend. This is the Yoshi who helped unite the abandoned Mario Brothers in SMW2, so it is probably safe to assume that Mario has a close bond with this particular dinosaur.

Yoshis communicate through their own language of grunts, "zips," and name repetition. Mario's Green Yoshi friend is the only member of the species that he is able to understand.

It is not entirely clear if there is such a thing as a "female" Yoshi, although it is interesting to note that male Yoshis seem perfectly capable of egg-laying.