"So what is Marxism? Do I fit in here?"
It is ok if you are not a 10th degree grand master of Marxonomics, all you have to have to be welcome here is respect for the community and a willingness to learn. We will teach you.
Marxism is highly complex however the basic concept of it is:
Capitalism is fundamentally flawed, isn't reformable, and requires a working class revolution to solve the constant revolving crisis' of capitalism.
If you agree with the above statement you belong here.
Marxism takes a scientific and pragmatic approach towards solving this issue (organize, educate, agitate) as opposed to an idealistic one (we'll just do a revolution and everything will be fixed!).
Welcome all new leftists! As per always, it is best to study works of our most successful comrades (Marx, Engels, Lenin, Stalin, and Mao) and their works can be found at Marxists.org for free.