Zerg unit production locations
The technology tree, or tech tree is a hierarchical visual representation of the possible building sequences a player can make, in accordance with a selected strategy, build order, or "Meta". These sequences thus unlock and enable various new units or abilities/research upgrades for use as the game progresses.
The diagram is tree-shaped in the sense that it branches at certain intervals, allowing the player to choose between one of several building sequences in terms of, with the process continuing iteratively further down the tree for additional technologies. Typically, at the beginning of a game, a player may only have a few options for technologies to research. For example, the 
Protoss player will only be able to produce one unit, the Probe. Not until the player makes a Gateway will additional units be unlocked.
Each technology that a player researches will enable more options until that branch of the technology tree is exhausted at its end point, as in, for example, the Protoss Forge, which makes various research upgrades available, but without further unlocking of new units or spells.
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. During competitive play, players must often balance between "teching" and amassing attack units, as one can be caught off guard without sufficient defense or various (eventual intended) spells/units should an opponent time an attack to occur during the teching process. For example, in the Protoss vs Zerg match-up, the Protoss player may be careless in teching up without sufficient defenses by starting with a Gateway-first build, such that an aggressive Zerg player may exploit timing advantages to attack with speed-upgraded Zerglings before the Protoss player has the opportunity to build sufficient Zealots, Dragoons, or other defenses.
Presented below is a representation for Zerg focusing on the production buildings to indicate the location where each unit is produced, or what can be produced by a given structure. As such, it does not indicate the pre-existing technology that is required before production of a given unit.
Zerg Unit Production Locations
