Locate the gerund (not the gerund phrase) and identify its noun use.

Talking too much is my chief problem.

Gerund:

Noun Use:

In the sentence "Talking too much is my chief problem." The gerund is Talking, and its noun use is subject.

Gerund is a word ending in ing that is made from a verb and used like a noun, and has the same form as the present participle (working, speaking etc.). I can be used as subject of a sentence (Reading French is difficult.), as complement of verb (His hobby is painting.) etc. Gerund functions like a noun.

Gerund: Talking

Noun Use: Subject

It is gerund because of the - ing