"I dream about food."
Translation:Yo sueño con comida.
In English as well, a root verb + an adverbial preposition/adverb often has a different meaning than the root verb when it stands alone. For example, compare "I go" with "I go up," I go down, I go with, I go to, I go from, I go out, I go under, I go over," to add but a few prepositions that change the meaning of the root verb. When these adverbs (and they are considered both parts of speech–adverb and preposition) are added as a sort of "inflection" of the verb, they are called particles. In English, root verbs plus articles can be used as gerunds, participials, and infinitives. I am not sure, but I believe it may be the same in Spanish.