The periodic table of the elements places the elements according to their atomic number, electronic configuration and chemical properties.
Thus, depending on the location of an element in the periodic table, we can guess its electronic configuration and more importantly, its properties. For example, if an element belongs to the group of halogens, we can determine that it needs 1 more electron to fill its outer orbital and achieve a fully-filled electronic configuration. We can also tell that it is a non-metal and readily accepts an electron. Additionally, we can predict the type of reactions it will undergo with other elements. For example, halogens react very readily with alkali metals (such as potassium, sodium, etc.). We can also gain some idea about the properties of the compounds an element will form by knowing its location in the periodic table.
Hope this helps.