The preposition para is contracted, most of all in informal situations, to pra.
pra for para
Eu vou pra Copacabana. <=> I go to Copacabana.
Este livro é pra mim? <=> Is this book for me?
Pra que você quer isso? <=> What do you want this for?
In Brasil pra can fuse as well with the article. One could believe that pra + a receives an accent like a + a = à. However this is not the case. Concerning the use of articles together with geographical names see 18.104.22.168.
pra (para) + a
Meu irmão foi pra Alemanha.
Meu irmão foi para a Alemanha.
=> My brother went to Germany.
pra (para) + o
Você vai pro Rio de Janeiro de férias?
Você vai para o Rio de Janeiro de férias?
=> You go to Rio de Janeiro on holidays?
pra (para) + as
Essa comida é pras cantoras?
Essa comida é para as cantoras?
=> Is this food for the singers?
pra (para) + os
Você trouxe café pros diretores?
Você trouxe café para os diretores?
=> Did you brought the directors the coffee?
Basically prepostions and conjunctions do the same thing. Preposition describe the relationship between two objects, conjunctions describes the relationship between two more complex ideas described in sentences, the main clause and the subordinate clause. I may seem strange at first glance, but the relationships between two objects can be more diffus then relationships between two actions / events and therefore we have a higher degree of arbitrary in prepostions than in conjunctions. To put it otherwise: If the relationship between two objects is diffus, the linguistic usage is instable, it is possible that different prepositions are used in the same context, because no prepositions fits really with the context or is unequivocal. In general we have a one to one relationship in conjunctions. To any conjunctions in one language corresponds one conjunction in another languages that is used in both languages if the contexts are the same. The relationships described by conjunctions is limited: adversativ, concessiv, temporal, causal, conditional, final and modal, see 19. The relationship between two objects is very often unclear. In English we say the painting is on the wall. Actually, if we assume a two-dimensional space, it is in the wall. The apple don't hang on the trees, they hang in the trees. We understand without any problem that the relationship between wall and painting at one side and apple and tree on the other side is very different. Using the same preposition in both cases can't be correct. It is only correct because there is no preposition at all that really fits and therefore we can say just anything and the actual use is just an unconsciously made agreement.
The basic meaning of para is for. More or less precise the relationship between two objects can be described like this. For / para describe a relationship between two objects where one object is incomplete and requires something provided by the other object.
He does it for him.
We buy tinsel for the Christmas tree.
He spend his money for useless things.
Nobody knew what that is needed for.
Para ela não havia dias feios, o sol sempre estava brilhando em algum lugar.
Bad days didn't exist for her, somewhere always the sun shined.
Estou procurando um quarto para duas pessoas em Lisboa.
I am looking for a room for two persons in Lisbon.
Preciso deles para um trabalho em Florença.
I need her for a work in Florence.
A escola irá enviar-lhe uma carta de convite para o curso.
The school will send you an invitation for the course.
However para can mean as well to and sometimes it is not translated at all.
Ir para o trabalho de bicicleta ou a pé não é algo muito comum no Reino Unido.
It is not usual in England to go to work by bicycle or by foot.