Jig hooks and the slotted tungsten beads commonly used with them are a relatively new trend in fly tying and fishing. Flies tied using them tend to ride in a more horizontal, hook-point-up orientation than standard bead head flies tied on straight-shanked hooks.
Most jig hooks have a 60 or 70 degree bend about an eye-length space behind the eye, and are usually barbless and extremely sharp. The beads are frequently made of tungsten to help the fly sink as fast as possible.
It’s important to match the correct bead size with the correct hook size. You may want to brush up on your fractions before making a bead purchase, unless you’re buying them from outside the United States, where they’re thankfully measured in millimeters rather than fractions of an inch.
Slotted beads are specifically designed to go with jig hooks and have a round hole at one end and an asymmetrical slot on the other. Standard beads look a little wonky on a jig hook whereas a slotted bead will rest correctly.