Neither is a rebate, both are tax credits. The $7,500 credit is the current credit.
The $12,500 is the proposed TOTAL credit in the House version of the budget bill and would completely replace the $7,500 credit. It is composed of several separate credits that will total up to $12,500 based on whether a vehicle qualifies. Right now there is a proposed MSRP cap of $74,000 on pickup trucks, with lower caps for other vehicle classes, in order to get the new credit.