When it comes to the objects they take (see object pronouns), verbs come in a wide variety of forms. When a verb is used without any objects, it is called intransitive.
A few verbs are always intransitive. Usually though, intransitive verbs can also be transitive (taking an object).
Il monte. He climbs.
Il monte les valises. He brings up the baggage.
When no preposition precedes the object, it is a direct object. If the object is introduced by à or at times pour, it is an indirect object (Indirect & Direct Objects).
There are other prepositions which can follow verbs and precede objects- the most common being de. (Preceded by 'de')
Ils parlent de la décision.
They speak about the decision.
Some verbs can take both direct and indirect objects (Ditransitives). Verbs never take two direct objects- at least one object must be preceded by a preposition.
Le chien a mordu Paul à la jambe.
The dog bit Paul in the leg.