A tech is any advanced maneuver, exploit, or technique that goes beyond a beetles basic moveset. The vast majority of players playing the game utilize tech to help win with it being essential in order to move around quickly on the map.
The most basic tech that is used in every match by all players at most levels of play is a Momentum Transfer. This is used to transfer momentum gotten from a source such as gliding, into movement with the ball, allowing you to cross the map much quicker than you would if you were just sprinting.
A large amount of essential tech is available to all beetles while beetles each have their own specific tech as well. Certain beetles rely a lot more on tech than others (such as Long-nosed Weevil) while other beetles have more focus on their base abilities (such as Tiger Beetle).
Green stars in the chips below mark any tech that is essential to learn. Yellow stars are tech that can be good but aren't essential to play well at high levels of play. Red stars are tech that are useless in a match while gray stars are tech that used to exist in the game but were removed (but are still listed here due to being heavily mentioned).