How to read ASH Report

Hi All

i have put (...) for readablility, don't know yet any other way to make it readable.

Event                               Event Class     % Activity   Sessions
----------------------------------- --------------- ---------- ----------
db file sequential read             User I/O             81.34       0.96
CPU + Wait for CPU                  CPU                  12.97       0.15
log file sync                       Commit                2.12       0.02
          -------------------------------------------------------------

what does CPU + Wait for CPU means here?

what does 12.97 means?

what does db file sequential read means here?

what does 81.34 means?

Also if you can explain following too:

    SQL ID    Planhash % Activity Event                             % Event
------------- ----------- ---------- ------------------------------ ----------
abg1napandmg4  2354793776      54.68 db file sequential read             50.25
SELECT ELEMENT_NAME ,SUM ( PRRV2.RESULT_VALUE ) HOURS FROM PAY_RUN_RESULTS PRR ,