BREAK: The SKIP clause is part of the BREAK command.
ON column_name: This tells SQL*Plus which column you are working with. The subsequent SKIP clause applies to this column.
SKIP: The SKIP keyword introduces the skip clause.
PAGE: If you use SKIP PAGE, the result is a page-break whenever the column's value changes.
line_count: If you do not want a page-break, then specify a number here. When the column value changes, SQL*Plus will advance the specified number of lines.
The entire line containing the second "ON" clause: You may list as many columns as you like in the BREAK command.