Rim Joist

In the framing of a deck or building, a rim joist is the final joist that caps the end of the row of joists that support a floor or ceiling. A rim joist makes up the end of the box that comprises the floor system.

The header is to a rim joist what the top or bottom wall plate is to an end stud.

Joist End

The end of a floor joist is often a tricky place to insulate.  It can sometimes be efficiently insulated with a fiberglass batt. Quite often spray foam insulation is best due to the limited space and access.