What is the difference between por and para?

Early on in your Spanish studies para is used much more than por, but the more advanced that your writing and speaking becomes the more you need to know to distinguish between the two!

Para is most commonly used to mean 'in order to' before an infinitive verb e.g. yo leo un libro para mejorar mi vocabulario (I read a book in order to improve my vocabulary)

It is also used to express destination e.g. voy para Madrid (I'm going to Madrid)

It indicates a recipient of something e.g. el regalo es para tí (this present is for you)

To express a deadline e.g. los deberes son para lunes (the homework is for Monday)

Por has many more uses than para, as well as being used in many idiomatic expressions such as por supuesto (of course)

To express gratitude and apology e.g. gracias por la cena (thank you for dinner)

It is used for both multiplication and division e.g. 10 por 10 es 100 (10 times 10 is 100)

It means through or along e.g. andamos por el parque (we walk through the park)

For an exchange, for example of money e.g. Te doy 10 euros por el libro (I give you 10 euros for the book)

Other uses include: for means of transport or communication, on behalf of someone, to express cause or reason.

If you learn when to use para you can assume that por is to be used on the other occasions!