Bloom strength is a standardized test value describing the firmness of a gelatin gel made and measured under controlled conditions. A higher number indicates a stronger gel in that test. It is useful when comparing products for confectionery and desserts.
It is not the same as blooming gelatin, which means hydrating it before use. Gelatin sheets and powders can differ in weight and strength; use the manufacturer's conversion guidance rather than assuming one sheet equals a fixed amount of every powder.
Reference: Further reading.