What is a ptotstar?

A "ptotstar" appears to be a typographical error or misspelling. If you meant "protopstar," it refers to a young star that is still in the process of formation, typically found in molecular clouds. Protopstars are characterized by their accumulation of mass from surrounding gas and dust, and they eventually evolve into main-sequence stars as nuclear fusion begins in their cores. If you meant something else, please provide more context!