Its not a point entity (one that you place like a prop) It's a brush entity, one that you create like a brush, cover with the toolstrigger texture, and then tie to an entity with ctrl+t. Once thats done, you can change it to trigger_capture_area in the drowdown menu in the window that will pop up.
Trigger_something entities are brushes, as are func_somethings. Most other things are point entities- prop_something, point_something, env_, info_, and logic_ are all points.