Pumping your item gas just means putting fuel in your vehicle yourself instead of letting an attendant do it for you. You're not allowed to do it yourself in Oregon and New Jersey (with, I believe, some exceptions to ensure people can still acquire fuel in circumstances where it's unreasonable or impossible to have an employee to do it for you.)

In the United States, most adults outside dense (or well-planned) cities own their own gas (petrol) powered vehicle. In most places, you go to a gas (petrol) station to refill the tank. In some states, it's illegal (for liability reasons) to do this refilling yourself. An attendant has to come around, collect payment, and refill the tank for you.

All the gas stations in OR are full-service, that is, an employee of the gas station will fill your gas tank for you.

I think that's literally about putting the gas line into your tank and pressing the trigger...