Matter is all around you. Now I would like for you to tell me some examples of matter here in our room. All the things you have named are forms of matter. Matter had different forms. One form is solids.
Solids have a definite form.
That form usually doesn't change. Another form of matter is liquid. Liquid changes shape depending on what is holding it, but doesn't change size. The last form of matter is gas. Gases have neither a definite shape nor size.