What does it mean to be "rated"

An example is at the high limit blackjack were I play (Mountaineer in WV and Presque Isle, PA) they have a min and max bet for each table that is electronic.

Typically $50 min $2000 max. But then there is a plastic sign that says "Max bet for Non-Rated player is $1,000"

I have never had the $1000 max vs $2000 max issue come up, any time I have wagered over $1000 they either paid me, took my money, or pushed me, never any question. I assume by this action I am "rated."

I went with a friend who had never gambled at the casino before, and did not get a players card. We sat at the $50 min table and played a few shoes. He was hot and bet $500, got a blackjack, and bet the $1250 on the next hand, and won again, tried to bet $2500, was told the max was $2000, he bet it, pushed, then left the bet out and lost. Can I assume he was also "rated."

Any definitions would be helpful.

To be "rated" simply means to be known for typically betting at a certain level or dollar amount.
For example, if you typically bet $50 a hand at Blackjack, the floor supervisors who are familiar with your action will know you - or rate you - as a "$50 Blackjack player."
This rating is used to assign or dispense comps, or complimentaries, to you as one of their patrons, such as movie or show tickets, dinner or buffet passes, etc.

This is different than the table or machine limits, which indicate the betting ranges allowed for that table or machine.