There are three states of matter solids, liquid, and gas.  Solids have a definite shape and volume except for rubber, liquids have a definite volumes but no definite shape and flow.  Gases have no definite volume or shape and  they flow,  most gases are invisible to the eye.  Their is a fourth state of matter but it is very rare on earth , it is plasma.  Plasma only survives at very high temperatures,  it  is found inside the sun and in other stars too.  Plasma on earth can be seen in neon lamps and a few other things.