Object pronouns -direct and indirect object pronouns- substitute the noun. In English these are ‘me’, ‘him’, ‘her’ and so on. For example, in the sentence ‘Give Sam the pen,’ Sam is a noun, which can be changed to ‘Give her the pen.’ In Spanish the pronoun either comes before the verb as a separate word or after joined with the verb, when are used with affirmative imperative, an infinitive or a gerund. For example:
Le da el boli (he is giving her the pen).
Voy a darle el boli (I am going to give her the pen).
‘Dale el boli’ (give her the pen).
Estoy dándole el bolí (I am giving her the pen).