Matter is everything. From air to water to rocks, and even you. There are three common states of matter. Liquid, like water. Gas or vapor, like steam.
All matter is the same because all matter is made up of atoms.
Matter is also different because objects can be made up of different kinds of atoms. Gold is made of one kind of atom-gold atoms. Salt is made up of two different kinds of atoms-sodium atoms and chloride atoms. So you made it to the section that really matters. Anything that takes up space or has a mass of any kind is matter.