Length is the first thing that decides whether a dress works on you. Here is what each one means in practice.
Anything finishing above the knee. Reads as evening or weekend rather than office, and works best where the dress has some structure to hold its shape.
Between the knee and mid-calf — the most versatile length, and the one that carries from a desk to dinner without changing.
Ankle or floor length. Best in fabrics that move; heavier fabrics at this length need a slit or a panel to walk properly in.
Length is measured from the shoulder, not the floor, so the same dress falls differently on different heights. Every GoGurll listing publishes that measurement so you can compare against something you already own.