Collators produce parachain blocks and send them together with a proof-of-validity (PoV) to Relay Chain validators for validation and finalization. Collators do not need to be trusted because the security of parachains comes from the Relay Chain validators.
Collators are, however, necessary for availability and their operation comes at the cost of infrastructure and maintenance. To keep a healthy market for collator operation, Integritee Network accepts treasury proposals where expenses must be detailed transparently to get reimbursement in TEER.