Parallel play
Parallel play is one of four stages of play observed in young children and first codified by Piaget in the 1930s. These four are Solitary play, Parallel play (alongside but not with), Associative play (playing and sharing together), and finally cooperative play (different complementary roles; shared purpose). Of course all four forms of play persist into adulthood. Parrallel play is, usually, first observed in children of ages 2 or 3; while younger childre than that tend to play by themselves (solitary play). Older children interact with each other more (group play).
In education, parallel play also describes activities where students are divided into pairs or small groups and work on the same activity simultaneously. This gives all students equal opportunity for active involvement and reduces the exposure. (Since all students are playing, none are watching.)
Parallel play is also sometimes observed in older children when playing video games, particularly handheld games.