The preposition is an invariable part of the sentence that establishes a relation between two words. They don't have a meaning of their own and show position, time, relationship, etc. between words.
Examples of the construction
verb + preposition are shown below:

Soy de Guatemala.
I'm from Guatemala.
Trabajo con los caballos.
Then are coming from Mexico.
Corrimos hacia su casa.
We ran to his/her house.
Ella guía a los niños en el zoológico.
She guides the children in the zoo.
Mario viaja por Cartagena.
Mario travels through Cartagena.
Las podemos llevar hasta su carro.
We can take them to their car.