The present participle in Italian is used to express an action that takes place in the moment in which the person is speaking, and the person wants to underline that it is happening at that moment.

For example, if you say "Io studio l'inglese" it sounds like you are saying what you're studying in that period, or at school, it is kind of general. But if you say "Io sto studiando l'inglese" it sounds like you're studying English in that exact moment.

Anyway, in some situations they can both be used.

I hope I have expressed myself well:)