Offer is an offer... you are invited to join a company bla bla bla with salary bla bla bla..
Letter of employment: the above named individual has been employed in the following role from that date to that date with salary XXX and performed the following duties.
the offer of employment letter is the one given before joining
and
Letter of employment is the one given during the service which confirms your being an employee with your details of joining date, job duties, hours of work, salary etc
the offer of employment letter is the one given before joining
and
Letter of employment is the one given during the service which confirms your being an employee with your details of joining date, job duties, hours of work, salary etc
In simple words Employment letter is your work experience letter with company you are working for including job duties, and offer letter at this time means they will provide you job with same duties and post even after you will get your PR