1. Continuous progressive.
when we talk about something right now.
Is expressed with a form of be together with the present participle of the verb.

2. Subject - object
the subject usually comes before the verb.
the object usually comes after the verb.

3. After preposition.

as a preposition followed by a noun.
as an adverb without a following noun.

4. Adjective.
They respond as it is.

5.After some verbs:
use the gerund