Everything is made up of matter, But for every particle, there has to be an equal and opposite particle. This is what Antimatter is.
So, if you have an e+, you also have to have an e–, and so on for other sub-atomic particles.
The opposite particle will have the same features of the other particle but will have a different charge.
When an Antiparticle meets a particle, they destroy each other.
Watch the video below to learn more: