This is projective/narrative play. In this stage you will see more story and detail emerging in their play. This is small world play where they will have the little toys/trains/dolls/teddies etc talk to each other and create relationships/scenarios and worlds in their play. This stage of play is really important for social skill development. To have 2 (or more) toys talk to each other, they have to be able to consider a situation from two perspectives at once. This is the way they develop and deepen their empathy.  It is also through this play that they engage in problem solving, solution focused thinking, critical thinking, reciprocity, turn-taking and general civility (not that they nail it at this age, they are developing and deepening their capacity for these all-important life skills).