Along with the gerund and participle, the infinitive (cantar) in Spanish, as in English, is an nonfinite verb form (does not express person, number, tense, or mood) that can be used as a noun (nominal infinitive) or as a verb (verbal infinitive).

According to El buen uso del español, the two types of nominal infinitives are those of lexical nature and those of syntactical nature.

Nominal infinitives of lexical nature could be considered false infinitives because dictionaries classify them as nouns. They may be modified like nouns and be used as plurals.

Los románticos atardeceres en la playa.

Some examples of nominal infinitives are amanecer, andar, anochecer, atardecer, cantar, haber, parecer, pesar, poder, querer, saber, sentir, and ver.

Nominal infinitives of syntactical nature are those that occasionally function as noun phrases:

Ese eterno romper de las olas sonaba por toda la playa.

Verbal infinitives function as verbs, so they take direct and indirect objects and other complements, may appear with an explicit subject, and admit passive and compound forms as well as periphrases.

Al haber encontrado (compound tense) ella (subject) una nueva ilusión (direct object).