A fabulous artist Kimberly Roger of Numinosity Beads has written a great blog post about glass frit and it's various used in bead making.
You can find her post here:
I love frit due to the variety of applications you can use it for. You can layer it on your bead and melt it in completely, leave it partially raised or even encase it with a transparent color or clear. It can be used a s a background like on my first bead shown in this post or as a main design element.You can even use it on metal! Frit can be used in a multicolor mix or a single color. There are also color changing frits.
You must be careful when using frit as there is almost always some powdered glass in the bottom of the container. If it becomes airborne you must leave the room as it never can be cleared out of your lungs once breathed in. A special mask is recommended to be used when working with frit as well as a good ventilation system in your studio.
Here are some sets of my beads that I use frit to create. There are so many various applications. It is one of my favorite bead decorations! Check out my beads in my Etsy shop where everything is 20% off right now!