-am and -em
I'm not sure of the difference of these endings to some words.
For example: chegarem and chegaram. Foram and forem. Is there an actual difference in grammar or are they just two different words.
Could someone please explain this? Thank you :)
They are the same verbs in different tenses... chegaram and foram are "past", conjugated for the 3rd plural person. Chegarem and forem are also conjugations for the 3rd plural person, but in subjunctive (here you find a brief explanation about that:http://www.duolingo.com/comment/637703
They are the same verb, but in different happening time. It depends on when it happens. For example, I could say "eles chegaram" (they have arrived) and "quando eles chegarem" (when they arrive). Like "arrive" and "arrived", they are the same verb, but in different periods of time.