Yo= I, and estudio/estudia= Study, so Yo estudio this meant "I study"
Tu= you, so Tu estudias this means "you study" or "do you study" you cant use the word estudio here though because then it would change the phrase to "your study" so estudia is more appropriate to use.
El means "the" estudia el estudia making it "the study"
nosotros means "we" so that would go with estudiamos, because estudiamos means "we study" nosotros estudiamos
ellos means "they" so this would go with estudian, because estudian means "they study" ellos estudian
