A physical change is one involving a change of state, such as solid to liquid. It is a change that does not change the fundamental nature of the material. An example would be melting ice into water.
A chemical change involves a chemical reaction that changes the nature of what you are combining or separating. An example would be combining (in the propper ammounts) Hydrochloric Acid (HCl - a highly corrosive acid) and Sodium Hydroxide (NaOH - a very caustic base) both of which you need special equipment to handle, results in a drinkable solution of salt water. Another example is applying electricity to water, which breaks down the water into Hydrogen and Oxygen.