In terms of turkeys, a "hen" is a mature female and a "jake" is a young male. The immature jake does not exhibit many of the characteristics of a mature male or "tom," but rather resembles a hen, so it's helpful to be able to distinguish between a hen and a jake, especially when hunting wild turkey. Depending on where you hunt, it may be illegal to kill turkey hens, so knowing the difference between a mature female turkey and a young male is crucial.
Look at the breast feathers of the turkey. A male turkey, including a jake, will have black tips on its breast feathers. A hen will have brown tips.
Inspect the leg length from where the leg starts at the body to the middle of the top of the foot at the base of the toes. The leg length of a jake will be longer than the leg length of a hen.
Look at the fan of the turkey when it's spread. The feathers in the center of the fan of a jake will be longer than the rest of the feathers in the fan. The hen's fan feathers will be the same length.
TL;DR (Too Long; Didn't Read)
When in doubt, don't shoot at a wild turkey that you can't identify as a male, unless it's permissible in your area.
The presence of a beard or spurs is not a reliable indicator of whether the turkey is a jake or hen. While not common, hens can have a beard and spurs.