Hi Samith...
Compensation means the entire package that is paid to an employee, which includes all monetary and non monetary emoluments i.e. salary, pf and other such benefits.
Rewards is one part of Compensation, its a process which helps in reinforcing the behaviour, in a lay man's language reward is a monetary or no monetary recognition given to an employee in lieu of better performance.
Hope this answers your queries, let us know if you have any other such doubts.
Regards,
Archna