As it can be easily understood from the name, this part of the menu deals with tables which can be inserted into your document. Inserting the table can be also accessed form Insert menu, and several formatting options exist in Format menu, but Table is the core place to deal with tables in your doc. You should use it to Insert and Delete the table Rows and Columns as well as tables themselves. Merge and Split cells easily with the relevant features.
More advanced options are converting table-to-text, vice-versa, and sorting.
Add formulas to your table – a simplified version of MS Excel is already inside the Word!