The periodic table arranges the elements into families and periods (vertical and horizontal rows). The elements in each family have similar properties. As you go across a row, the properties vary gradually from one element to the next. The table tells you what elements may have similar chemical and physical properties.
The periodic table describes the atomic structure of all known elements. For instance, by looking at the periodic table, you can find out the atomic mass and the number of electrons the element has. Each element has its own separate set of such data. No two elements are the same.
This is perhaps the most useful feature of the Periodic Table. It is an excellent reference tool. In one place, you can find many properties of an element.