Table Enables to capture data in Tabular Form, Tables works as sub-forms in Doctype form view, by configuring fields in the table you can add columns in Table and User can add multiple rows in each data table, Use Configure Table Columns button in Field Editor of the Table to Manage Table fields,
In Doctype Editor, Drag and Drop "Table" Field from left side panel to editable area
Open Field Editor for Table field (Click on "Edit" icon, beside Table field ,"Edit" icon will appear on mouse-over to the field in Doctype Editor)
Click on "Configure Table Columns", to Add or Configure Columns (Fields) in Data Table.
On clicking "Configure Table Columns" Button, you will be landed to new form editor window similar to Doctype editor, here you can drag and drop fields to configure your table columns.
Table Editor will autosave your changes, to go back to Doctype editor - Click on "Close" button in Table editor.