When you add a table, its name (Table 1, for example) is shown by default. You can edit the name or hide it. No tables in a spreadsheet can have the same name.
Click the table, Control-click the row number for row 1, then choose Hide Table Name or Show Table Name.
Triple-click the name at the top of the table, then type a new name.
To enclose the table name in a border, click the table, then in the Format 
sidebar, click the Table tab. Click the Table Outline pop-up menu, choose an outline style, then select the “Outline table name” checkbox.
To add a caption or label to a table, see Create a caption for an image or other object.