Gerunds express the action of the verb as if they were an object. Thus, for example, one could say:
- Reading teaches you many things.
In that sentence, the verb "to read" is converted into a gerund, "reading", which then functions as the subject of the sentence and so acts like a noun.
Gerunds can function as verbs within a dependent clause; in this case, the clause as a whole functions as a noun.
- Reading Conservapedia teaches you many things.
In that sentence, "Conservapedia" is the direct object of the gerund "reading". The entire clause "Reading Conservapedia" is the subject of the main clause in the sentence.