TTITLEcommand was continued to the second line.
COMPUTEcommand here tells SQL*Plus to calculate the sum of the TOTAL_SALE column when there is a break on the LASTNAME column.
BREAKcommand here says that the report will break on each new value of the LASTNAME column and then skip one line.
TTITLEcommand said to place these words, left justified on the first line of the report and then skip one line (meaning go to the next line).
TTITLEcommand (second line of the command) stated to print "Pg."
TTITLEcontains the SQL*Plus variable called SQL.PNO. This is one of a small handful of pre-defined variables within SQL*Plus.
TTITLEsays "SKIP 2" at the end of the command.
BREAKstops printing rows and the
COMPUTEcommand prints its results (the sum of TOTAL_SALE).
BREAKcommand (SKIP 1). After this line, the next row of the report is printed.