With the preposition de and a, the article merges el to del and al
Marcos sale del cine a las diez por la noche
Quiero ir al zoológico
Use of the definite article
As a rule, the definite articles “el,” “la,” “los,” and “las” are used in terms that refer to concrete or known things.
The indefinite articles un, una, unos, unas, on the other hand, are used for terms that have not yet been mentioned (new) or are any person or object.