What does trust do in Palworld?

Short answer

Trust is a 10-rank friendship stat that raises a Pal's HP, attack, defence and work speed as it rises.

Trust — the game’s friendship stat — runs from -3 to 10, and each Pal carries its own bonuses to HP, shot attack, defence and craft speed that scale with it. Those per-Pal friendship bonuses are in the character table alongside the base stats.

The ranks are not evenly spaced. The steps widen the whole way up, so the last few take far longer than the first few — and negative ranks exist below zero, which is what mistreating a Pal costs you.

Rank	Points needed	Step from the last
-3	-10,000	—
-2	-1,000	9,000
-1	-1	999
0	0	1
1	6,000	6,000
2	13,000	7,000
3	21,000	8,000
4	30,000	9,000
5	40,000	10,000
6	55,000	15,000
7	80,000	25,000
8	110,000	30,000
9	150,000	40,000
10	200,000	50,000