F1 (filial 1) is the first generation produced by crossing two distinct, true-breeding parent lines. Both parents must be stable — meaning their offspring consistently express the same traits. Cross two such parents and you get F1.

F1 hybrids exhibit what's called hybrid vigor (heterosis): unusually consistent expression, faster growth, and stronger plants than either parent alone. This is why F1 packs are popular with commercial growers — the plants are predictable.

Important: an F1 cross is only a true F1 if both parents are stable (typically IBL — inbred line — or landrace). If one parent is itself a hybrid or polyhybrid, the offspring is more accurately called an F1 polyhybrid, and the consistency is reduced.

Selfing or crossing F1s together produces F2 — and F2 is where the recessive traits scatter, opening up phenotype hunting and selection work.

Is every F1 the same?+
Among true F1s, plants are highly uniform — that's the point. Among F1 polyhybrids (where the parents weren't stable), variation is still significant.
Are F1 seeds better than F2?+
Different jobs. F1 is for predictability and uniformity. F2 is for phenotype hunting and breeder selection work.