Full-service just means it's dispensed by an employee rather than by the pilot. (The practical implication is "you can buy fuel only when the business selling fuel is open, or pay a call-out fee".) This could be dispensed from a fuel truck (most common for full-serve) or from a pump.

Self-service means there's a pump with a credit card and a really long hose, that would look familiar to what you see at an auto filling station.