What's the difference between a service and an offer in freelancing?

[Btaliat]

Among the terminologies to know in freelancing is offer and service. There is a need to know the difference between the two of them. Service refers to what what you have offer as a freelancer, while offer is what you have done for your clients. There is a need to know when to use offer and when to use service for people to take you serious as a freelancer. Is there any difference that you know between them again?