They are synonyms. English has very few true synonyms, but those two words really do have exactly the same meaning and are used in the same way. Apparently, 'perhaps' is more common in written English and 'maybe' is more common in spoken English. 'Perhaps' could also be considered as slightly more formal, but there really isn't much difference. You can use either one in any situation.

Thank you Evie :) it's clear now

I would say that 'perhaps' is a more formal version of 'maybe'. 'Maybe' is often used at the start of a sentence or at the end, whereas 'perhaps' can be found in the middle, front and end of sentences. They mean they same thing though.