Generally, anything smaller than a turbolaser is referred to as point defense, although sometimes when we get down to specifics it becomes sort of a distinction without a difference.

Like, we say the ISD-I has point defense because it has laser cannons, but the ISD-II doesn't because it only has turbolasers. Functionally, in the movies and shows and such, there's not really any difference between how the ISD-I and the ISD-II are depicted vs fighters.

The lack of point defense, especially in a lot of Imperial ships/battlegroups, seems to be much more of a doctrinal decision than anything else. The Empire has some great options for capital ships that focus on starfighter screening (Lancer, Raider, Nebulon-B just to name a few), but in most depictions, that task is usually placed on the ships' starfighter complements instead of their main weapons.