The spots on a jaguar are called rosettes.
Leopard rosettes have fewer dark spots than Jaguar rosettes which have an additional dark spot in the middle.
Cheetahs are taller, more slender cats, with spots that have no rosettes, or circles. Jaguars resemble leopards, but are stockier built, with shorter tails. Jaguar rosettes are larger on the flanks.
a jaguar has no spots. Jaguars are completely black.
Jaguars are heavier, more muscular animals, and the spots on the flanks are larger rosettes.
Leopard
Usually just called spots, but around side and back of body are black spots that form a circular formation around a central spot called rosettes.
Each jaguar has a variety of spots in different sizes and shapes. The average jaguar has more than 100 spots or rosettes on its body.
The broken rosettes
The spots are called "rosettes". These rosettes provide camouflage, breaking up their shape when viewed against the textures and colours of their natural environment, aiding them in avoiding aggression from larger animals or aiding the stealthy hunt. While the above answer is somewhat correct, cheetahs actually do have spots while jaguars have rosettes.
Jaguar
Leopards are Old World cats, similar to the jaguar, although lighter built. Both are spotted normally, but jagaur spots are like rosettes on the flanks. Both can have black cats in their species.