Developmental scientists classify play into a number of different types, notably object play, physical play, and pretend play. Each of these can become forms of social play when they are shared with another person.
Each of these three general forms of play emerge in infancy, during the 12 - 24 month period.
The very first object play appears around a year. If you see your year-old child do something like pick up a phone, hold it to her ear and jabber, you are seeing the very beginnings of object play. Your child at this point is doing culturally appropriate things . . .