What is an example of a subatomic particle?

There are several subatomic particles. In general the term refers to the three main parts of an atom - the proton, the neutron, and the electron. But the proton and neutron are made up of even smaller particles called quarks (there are 6 of those!) and then there are all sorts of gluons and mesons... but I think the basic answer is the one that you want. Stick with proton, electron, and neutron.