It tells you what the paragraph is going to be about.
An F1 hybrid (or filial 1 hybrid) is the first filial generation of offspring of distinctly different parental types. F1 hybrids are used in genetics, and in selective breeding, where it may appear as F1 crossbreed. The term is sometimes written with a subscript, as F1 hybrid.
A hybrid is where the positive pin of the tank connects directly with battery, other mechs like the nemi have a pin (sprung or otherwise) between the battery and the atty. Your more prone to getting shorts with a hybrid unless you follow a few simple rules, main one is_make sure the positive screw of the tank is protuding at least 1 mm or 2 from the threaded part