Infinitive VS Gerund

The Basics:
Gerund: VERB + -ING (eating, going, studying)
Infinitive: TO + BASE VERB (to eat, to go, to study)

The main verbs (are they?)
A gerund is the present participle (-ing) form of the verb.
An infinitive is to + the base verb (the verb with no ending). Both gerunds and infinitives are action words (i.e., verbs) in meaning, but they act like nouns in the sentence.
They always take a noun position: a subject or an object of the main verb. A gerund or infinitive is never the main verb (e.g., I hiking and I to study are incorrect).
An infinitive/gerund

Find the Professor:
Skiing is fun.
I like hiking.
I need to study.
I enjoy watching movies.
I don’t want to study English.
I asked my friend to help me.

3 Gerund Rules:

1. Subject = Gerund
When you need an action as a subject, use a gerund. Infinitives are possible, but they are very formal and not very common in this position.
Reading is my favorite hobby.
Learning English has improved my confidence.

2. Preposition + Gerund
After a preposition, use a gerund. This is true for prepositions that are part of phrasal verbs, too.
I thought about calling my grandma, but I was too tired.
Are you planning on going to the party? (See the Notes section below to find out why planning is not a gerund.)

3. Verb + Gerund
A gerund or an infinitive can be used after a main verb. It depends on the verb, and there isn’t an easy rule for this case. Memorizing the most common verbs that take a gerund, such as advise, avoid, enjoy, finish, practice, quit, and suggest, is helpful.
My teacher advised studying for the quiz.
They enjoy making crafts in class.
*Don’t forget that some verbs take either a gerund or an infinitive with no change in meaning! Some common verbs include like, love, and hate.
She likes watching movies.
She likes to watch movies.

3 Infinitive Rules

1. Adjective + Infinitive
After an adjective, it is common to use an infinitive verb. A gerund is possible in some cases, but an infinitive is usually the better choice.
It is fun to play video games on the weekend.
It was helpful to learn these grammar rules.

2. Noun + Infinitive
If the main verb has an object that is a noun or a pronoun, it is almost always followed by an infinitive verb instead of a gerund.
Did you want me to call you?
The students asked their teacher to help them.
*Note: This rules is very helpful, because it is stronger than the “verb + gerund” rule. For example, the verb advise normally takes a gerund (She advised studying for the test), but a noun/pronoun object will override this rule (She advised her students to study for the test).

3. Verb + Infinitive
A gerund or an infinitive can be used after a main verb. It depends on the verb, and there isn’t an easy rule for this case. Memorizing the most common verbs that take a infinitive, such as ask, choose, decide, get, need, plan, promise, and want, is helpful.
He wants to learn Japanese.
We need to clean up this mess.
*Try typing in “gerunds and infinitives verb list” into a search engine to see lists of common verbs that take a gerund or an infinitive.