Spanish Preposition: A
This preposition is a tricky one, even for locals, because its use is ‘multimodal’ [multiple modes] One of the most important ones is to indicate who is receiving from who, i.e. in ‘el perro persigue al gato’ [the dog is after the cat] if you take it away you’ll get: ‘el perro persigue el gato’, and you can’t tell who is after who.
Sometimes you have to “take the ‘a’ away”, as in: ‘Antonio busca un sastre’ [Anthony is looking for a tailor] because if you add the ‘a’, as in ‘Antonio busca a un sastre’, then it means he is looking for a certain tailor he knows. In these instances ‘a’ gives personification to whatever follows.
Prefiero un albañil a un plomero
I prefer a mason to a plumber.