1) TA posits that people's thoughts and behaviors are influenced by their "ego states" - the Parent, Adult, and Child parts of their personality. Interactions are shaped by which ego states people engage with. 2) "Transactions" refer to any communication between two people, and can be complementary, crossed, or ulterior depending on whether the responses align with expectations. 3) People unconsciously send "strokes" or messages to each other through their communications and these can be positive or negative. Understanding transactions and strokes is key to TA's analysis of human interaction.