The English Gerund
The gerund is sometimes called a verbal noun, a name that better describes its use in a sentence. The English gerund is formed by taking the normal verb form and adding –ing to the end. However, this construction is used in three English constructions; in a verb phrase, as a verbal adjective, and as a gerund. Distinguishing these three uses of the same form of the verb requires much experience with the English language. Native English speakers, of course, use them without any trouble. For non-native English speakers, this anomaly of the language presents a very difficult obstacle to proper English grammar.
As part of a verbal phrase, the verb + -ing form of a verb helps indicate the time at which the verb takes place. For example, in:
John is walking to the store.
“is walking" is a verbal phrase indicating that the action is taking place right now in the current time.
As a verbal adjective, the verb + -ing form of the verb acts just like any adjective modifying a noun. For example:
John is a driving expert.
Here, “driving" modifies “expert" because it indicates which type of expert John is.
As a gerund, the verb + -ing form of the verb acts as a noun that can function just like any other noun in a sentence. For example, in:
Driving is a dangerous job.
“Driving" is a gerund because it is a verbal form acting as a noun in the sentence.