It's thinner than monofilament, so you can cast farther and more accurately.
The thin diameter also allows for easier use in smaller reels.
A braided line is much more resistant to abrasion and snaps, making it a great choice for using lures with sharp hooks or navigating heavy cover.
Braided line is good when fishing heavy water vegetation like lily pads, hydrilla, water hyacinths, and cattails. The braid will cut through the stems of most of these plants, keeping the fish from tangling you up, so you will land fish that you would lose with other lines.
Can be joined to mono line (see the image)