An ace is a serve your opponent never even touches — instant point. A double fault is two missed serves in a row: the point goes to your opponent without them hitting a ball.
Padel's controlled, flat overhead. You do not play it to win the point but to hold your position at the net when a lob drops too deep for a safe smash.
Cross-court means diagonal, down the line means straight along the sideline. The net sits at 91.4 cm in the middle — around 15 cm lower than at the posts — and the diagonal is a good metre longer.
The zone between the net and the baseline. You are too far back to volley and too far forward for deep balls, so you spend as little time there as you can.
In padel the ball bounces first, then you strike it below hip height into the diagonal box. In pickleball the rule is: below the waist, paddle head under your wrist.
A ball that lands in your court first may then rebound off your own wall and stays in play. Only a ball that reaches the wall without touching the ground first is a fault.
General
Terms from training theory that apply in every sport.
BMR is your basal metabolic rate at complete rest; TDEE is total daily expenditure including everyday movement and training. Nutrition targets always work off TDEE.