Definition:
gerund is a form of a verb that is always used as a noun. It is made by adding the suffix '-ing' to the verb. A gerund always takes the direct object of the verb, if any. It can be used as the subject of a sentence (e.g. 'Fishing is his hobby'), the object of a preposition (e.g. 'We are good at playing'), and as the complement of a linking verb (e.g. 'My religion is praying').
Rules:
Gerunds are typically used when the verb describes a habit, an activity, or an enjoyment. They are not used to refer to actions that are finished or occurrences that happen once.
Examples:
1. Learning French is an investment worth considering.
2. Teaching is her passion.
3. Shopping is so much fun.
Tips:
it is important to remember that gerunds are always used as nouns and not verbs. It is also important to note the spelling distinction between present participles (ending in -ing) and gerunds (also ending in -ing). While present participles are used as adjectives and used to describe nouns, gerunds are nouns in and of themselves. Finally, gerunds cannot be modified with adverbs.