There are three kinds of verbals: gerunds, infinitives and participles. All three kinds of verbals are words that are usually verbs but have been used as modifiers or nouns in a sentence thus changing their true part of speech to an adjective, an adverb or noun. Gerunds most often become nouns and end in "ing". Participles come in both past and present tenses and usualy become modifiers. Infinitives usually are spelled the same as their verb form, but are proceeded by the word "to".
Here are some examples:
Listening is the key to understanding. First, find the verb of the sentence. The verb here is the linking verb "is". Now ask - "Who or what is?" Listening is. Since "Listening is the key ..." it has become a thing. A thing is a noun. Listening is the subject of the sentence. Although a person can perform the action of listening, they way it is used in this sentence is as a subjective noun.
We love to stay at the Holiday Inn. Find the subject of the sentence by asking "who or what loves?" The answer is "We". We is the subject of the sentence. What do we do? We love. Since you already have both a subject and a verb for this simple sentence, what is "to stay". This is an infinitive! In this case the infinitive is acting like a direct object answering the question "what do we love"? Another verb has been turned in to a noun. In this case an objective noun.
The burnt cookies tasted awful. The word "burnt" is an example of an irregular past participle. You can burn cookies, but in this case the word burnt is an adjective describing the kind of cookies the person ate. The subject is cookies and the true verb is "tasted" (linking verb because the cookies didn't actually taste anything themselves).
