He identified three "ego states", the Parent, Adult and Child states, that co-exist in all people. He then considered how individuals interact with one another, and the ego states that were participating, both ostensibly and actually, in each set of transactions.
He sketched common stereotype sets of interactions involving ulterior motives, identifying these as "games". The first such game discovered was Why don't you, yes but in which one player (White) would pose a problem and the other players (Black) would propose solutions. White would point out a flaw in every Black player's solution, until they all gave up in frustration.
In addition to scholarly work, Bern wrote two popular books on transactional analysis, which summarize his ideas for the layman.
Popular books by Eric Berne on Transactional analysis: