Cells are the units from which plants, animals, bacteria, proctoctista and fungi are made from.  Viruses are not made from cells.  In plants, cells have a cell wall (as well as a plasma membrane), whereas animal cells only have a cell membrane.  In fungi the cell wall are made from chitin, and in plants it is made from cellulose.  What is interesting if that these molecules are very similar, and only simple changes in how they bond together makes them different molecules.

So, dogs, you, leaves, chimps, worms and most of the things you can think of have cells.

All living things are made up of cells--they are the basic building blocks of living things. Dog cells are animal cells; leaf cells are plant cells. There are some similarities and differences between the two. Plant cells have cell walls, which give the plant the ability to have rigidity and specific shapes. Animal cells do not--animals have specialized cells types for this function, such as bone and cartilage cells. The major difference, though, on which all life depends, is that some plant cells have chloroplasts. Chloroplasts are specialized organelles that turn the energy of the sun into chemical energy. This energy not only supports the plant, but animals that eat the plants. 

There's a lot more to it--see the below link for starters!