Matter is anything that physically takes up space and has mass. More specifically, anything that is made up of atoms is considered matter, which is everything.
Literally anything that can be physically touched, seen or felt is matter. The very screen on which this answer is displayed is made up of matter. Even the air is made up of matter because it is made up of nitrogen, oxygen and other elements, which are made up of atoms. Even some of the vast emptiness of space is made of matter because there are constantly light particles or radiation flying through space.