Dear Himani,
These words are not synonymous, as job satisfaction is a subset of employee satisfaction. An employee can be well satisfied with his job but not overall satisfied due to various other reasons. The job that the employee is doing may be good for him or her, and he or she likes the job, but he may be dissatisfied about something else in the organization, such as the process of performance appraisal, employee recognition, a bad boss, poor compensation package, etc.
Regards,
Byomjeet