The three states of matter are solids, liquids and gases. Matter is basically atoms, compacted or loose. A solid has compacted atoms so you cant just put you hand through a solid . Unlike gases and liquids, whose atoms are not stuck together, that means you can put your hands through and the atoms will depart.

 

An example of a physical change is a change that it can reverse, and transform or go from a solid to a  liquid or gas. Water is a example of this physical change. It can go from liquid to solid when you freeze it or it can go from solid to gas or steam when you boil it. It can do that cycle in any order.

An example of chemical change is baking. Say you add eggs, flour, and sugar together, you make a chemical change when you mix it. But once it is mixed it will never un-mix to get it back your eggs flour and sugar again.

In conclusion matter is just atoms compacted or far apart. Forms that atoms take change constantly, we change matter every day even with out noticing.  Matter is atoms, which are in everything so everything has atoms so every thing is matter even you(and yes you do matter)!