Overlock seams are the traditional stitched seams you'll find on budget-friendly cycling pants. They're created by wrapping thread around the fabric edges, which leaves a raised ridge on the inside of the garment. While this construction is strong and keeps costs down, that raised seam can rub against your skin during pedaling—especially in sensitive areas like your inner thighs.
For short rides under an hour, overlock seams are generally fine and won't cause major issues. If you're just commuting a few miles or doing a quick neighborhood spin, these pants can work without problems. However, for longer rides, that raised seam becomes a real chafing risk that can make your ride miserable.
If you plan to ride for more than an hour, it's worth spending a bit more for flatlock stitching, which lies flat against your skin and dramatically reduces chafing. Think of overlock seams as acceptable for casual, short-distance use—but not something you want against your skin on a three-hour weekend ride.