Service submission is not (necessarily) sexual submission. It tends to refer to submissives who perform services for their Dominant. The most common form is domestic service — cooking, cleaning, laundry, etc. But a service submissive may also do your taxes, mow your lawn, clean your pool, or fix your car. The act matters a lot less than the feeling behind it — being of service and making the Dominant’s life a little (or a lot) easier and more comfortable.