What does the periodic table show you?

The periodic table arranges all the different elements into columns and rows, The horizontal rows are called periods, this is where the elements differ from left to right but the addition of an electron to their outer shells. The vertical columns are called groups, elements in the same group behave similarly as they have the same amount of outer electrons in their outershells. Their are 8 groups from left to right with groups 2 and 3 housing the transitionmetals.