Your hold luggage will be checked in directly to your final destination, unless your layover is more than 24 hours (which is rarely the case).

Once you get off the plane, you can follow the "Transit" signs to clear security and proceed directly to the boarding gate; or you can clear immigration and customs to get out of the sterile area. Then you can just re-enter directly as long as you have a boarding pass and a travel document (passport). You would have to clear security as well as immigration again; allow around 1h for both although it's usually much faster.

If your layover is 5-6h or more, it might be worthwile to get out of the airport and see what's outside.

This is how it works in Taipei, and many other places. On the way back, if you have a connecting flight in the US, you will have to pick up your hold luggage and clear the customs (afterwards, it's collected back from you again).