When a dealer sends a vehicle to the auction, is that for other dealerships to bid on or can I bid on it also?

Yes. You can bid too.

Anyone can bid unless it's in a dealer ship only line

I've taken a vehicle or two there, plus I've also gotten a vehicle or two there to go to Value Auto Auction in Crooksville, OH It has been for dealers so far.

IT DEPENDS. IF THE SALE IS DEALER ONLY THEN YES. IF IT IS AT THE PUBLIC AUCTION THEN NO.