Tee
The small peg (usually wood or plastic) pushed into the ground to elevate the ball for a tee shot.
Height matters more than most golfers think: too high and you risk hitting the top of the driver's face for a pop-up, too low and you risk a thin, low shot. "Tee" can also refer to the teeing ground itself, the marked area where a hole begins.
See the full breakdown: Pop-Up / Sky Ball
Every common cause and fix for this exact issue.
See the full breakdown: Thin / Topped Tee Shot
Every common cause and fix for this exact issue.
More equipment terms
Loft
The angle of the clubface relative to a vertical plane, which controls launch angle and, largely, distance.
Lie Angle
The angle between the shaft and the ground when the club is soled correctly at address.
Bounce
The angle built into the sole of a wedge that helps it glide through sand or turf instead of digging in.
Offset
A design feature where the leading edge of the clubhead sits slightly behind the hosel.
Shaft Flex
How much a shaft bends during the swing, rated from Extra Stiff down to Ladies/Senior flex.
Cavity Back vs. Blade
Two iron head designs: cavity-back irons hollow out the back of the head for forgiveness, while blades (muscle backs) are more compact for feel and control.