Hi Steve, great question!
A feminized cannabis seed is a seed that has been modified, either naturally or chemically, so that it will always produce female cannabis plants. When you grow cannabis in the traditional way, in which the male plant pollinates the female, you will get about a half/half result of male and female seeds.
Feminized seeds are beneficial because female plants almost always sprout buds, whereas male cannabis plants are not guaranteed to bud. A popular way to feminize your seeds is to spray them with colloidal silver, then collect the pollen.
Would love to hear from others, experiences about feminizing seeds, tips, tricks, the works!