The technology tree or tech tree is an abstract hierarchical visual representation of the possible sequences of upgrades a player can take, by means of research. The diagram is generally tree-shaped in the sense that it branches at certain intervals, allowing the player to choose one sequence or another. Players only have a few options for technologies to research at the beginning. Each technology that a player researches will open up more options. The tech tree is the representation of all possible paths of research a player can take.
A player who is engaged in research activities is said to be "teching up," "going up the tech tree," or "moving up the tech tree." Analysis of a tech tree can lead players to memorize and use specific build orders.