They could put them together in groups that shared certain characteristics. The first to realize this was Johann Dobereiner. A pattern seemed to develop, that every eighth element shared properties. So they were called octaves. Dmitri Mendeleev was given credit for the development of the periodic table.
Families share many traits together.
For example, the right-most column are called the noble gases . All the members of this family are very inert, they don't react easily at all with other elements, due to their filled valence shell. On the other hand, the group next to that, called the halogens , are considered very reactive. All the elements on the left are metals, and if you go right, they gradually lose their metallicity at the steps. Another use of the periodic table is to find relative atomic sizes and electronegativities.