There are 92 naturally occurring elements together with several other man-made ones.
The elements are differentiated by their atomic number which is number of protons in their nuclei, balanced by an equal number of orbiting electrons. The table also gives the weights of the various elements in multiples of proton masses. The difference between the atomic number and the atomic weight is accounted for by the number of neutrons in the nucleus. Deviations from integral weights is accounted for by the ocurrence of isotopes. These are versions of the elements containing different numbers of neutrons.
The varying properties of the elements can be accounted for by the arrangement of the orbiting electrons and in particular the number of electrons in the outermost shell. It is these electrons which are involved in interactions with other atoms.
The atoms of Chemical elements interact with those of the same and other elements to form molecules. Molecules containing atoms of more than one element are called compounds. There are trillions of  compounds and it is quite impossible to provide a comprehensive account on them.
The commonest from of molecule is established by sharing electrons in the outermost shells in such a way as to make up the number to 2 for the first and 8 for all the others.
For example Hydrogen has one electron in its only shell. Oxygen  has 6 in its outer shell. Oxygen forms a molecule with two atoms of Hydrogen, completing its outer shell to 8. The result is water.
For further information see the following excellent Wikipedia entries:

http://en.wikipedia.org/wiki/Chemical_Elements

http://en.wikipedia.org/wiki/List_of_elements_by_symbol

http://en.wikipedia.org/wiki/List_of_minerals