Bridge Responders Jump shows a preempt or points...Playing Standard American
For questions about Standard American, you can always refer to the  Standard American Yellow Card System Booklet.

In this case, the booklet says that jump-shift responses are strong and slam invitational. The downside to the booklet is that it doesn't really cover followups for most bids.

Preemptive jump-shifts are quite popular among players who play a 2/1 system, but Standard American's inability to force to game at a low level makes slam exploration too difficult when responder holds a good hand with an excellent suit unless you play strong jump-shifts.