これは何ですか。

this (indicating an item near the speaker, the action of the speaker, or the current topic); this person (usu. indicating someone in one's in-group); now; here; I (me); certainly

topic marker particle; indicates contrast with another option (stated or unstated); adds emphasis

what; how many; you-know-what; that; whatsit; what's the expression; what do you call them; what?; hey!

be; is

indicates a question (sometimes rhetorical); or; whether or not; some- (e.g. something, someone); indicates doubt, uncertainty, etc.; emphatic prefix; suffix forming adjectives or adverbs; in that way