A closed system is a system in which matter cannot escape, but energy can. So performing a reaction in a container that is sealed with some type of lid or something. You know energy escapes, in the form of heat for one if you touch the container and it is hot or cold.
Now an isolated system would be in a container that is sealed and insulated in some way so that no energy or matter can escape. I don't think making a completely isolated system is possible, but it is possible to get extremely close.