The Calico, or Tortoiseshell, is not a breed of cat, but rather a description their markings. Their coats are a patchwork mixture of black, white, browns, and “tabby” orange.
The X chromosome determines the color of the cat, and since females carry 2 X chromosomes, Calico cats are almost always females, with one X chromosome passing one color and the other X chromosome passing another color.
Males have XY chromosomes, and since the Y chromosome does not pass color, there is little possibility of a mixture of colors. The occasional Calico male is nearly always sterile, with only about 1 in 3000 being able to breed. Still, they can not pass on the calico patterns to their offspring.
In many cultures, Calico cats are thought to bring good luck. We just think they’re cute.