Regular Unleaded Gasoline
100LL is standard aviation gasoline.
While LL stands for Low lead, it actually has more lead in it than automotive gasoline. The govt is making noises right now about substantially removing the lead from 100LL, which will remove some older aircraft engines from service and cause a lot of problems for the general aviation fleet. I expect hoarding and a black market of 100LL in the future if .govt does this.