I am taking a class at the moment.
Present continuous is used to talk about what you are doing now.
We form it by using the present form of the be verb with the ing version of the verb.
I am using a computer now.
All the rules for using be verb apply:
You are reading.
He is driving a car.
English sense of now does not necessarily mean right now. It can be something that you started earlier this week and will finish later in the week.
I am reading Harry Potter and the Philosopher’s Stone.
I’m not reading it right now but it is something I started reading earlier this week and will finish today or tomorrow. This is still considered something I am doing now.
I read fantasy novels.
This is the simple present. It means something I do regularly. In this case I regularly read novels in the fantasy genre.
You can use both simple present and present continuous to mean something similar.
I am taking English classes.
I take English classes.
These sentences are almost the same in meaning. The first one however suggests that it is something you recently started.
I am living in Mexico.
I live in Mexico.
These mean almost the same thing. Either one can be used. As in the above example the first one may suggest that you recently moved to Mexico. Another possible difference is when you are talking to a friend who doesn’t know you moved to Mexico and you are giving them new information about what you are doing.