Circular knitting, also known as knitting in the round, is a technique used to create seamless tubes of fabric. Instead of working in rows back and forth, you work in a continuous spiral, which is ideal for projects like hats, socks, sleeves, and even sweaters.

To knit in the round, you can use either double-pointed needles (DPNs), a long circular needle with a flexible cable, or a set of short circular needles designed specifically for small-circumference knitting. Here's a basic overview of how to start:

Cast On: Choose your preferred method of casting on stitches. You can use a long-tail cast on or any other method you're comfortable with.
Join: After casting on the required number of stitches, make sure they're not twisted around the needle. Then, join the last stitch to the first one, being careful not to twist them. This creates a continuous loop of stitches.
Begin Knitting: If you're using circular needles with a flexible cable, slide the stitches to the other end of the needle so the working yarn is at the right-hand needle tip. Then, start knitting stitches from the left-hand needle onto the right-hand needle.
Round Marker: It's helpful to place a stitch marker at the beginning of the round to mark the start of each round. This helps you keep track of your progress.
Continue Knitting: Knit all rounds (if you're doing stockinette stitch) or follow your pattern instructions for any other stitches or stitch patterns.
Joining in the Round: If you're using double-pointed needles, divide your stitches evenly among three or four needles (depending on your preference) and use the fourth needle to knit. Make sure there are no gaps between the needles.
Increasing and Decreasing: To shape your work, you can use various increasing and decreasing techniques as you would in flat knitting. Just make sure to maintain the pattern or stitch count required for knitting in the round.
Finishing: Once you've completed your desired length, you can bind off the stitches using your preferred method. If you're knitting a hat, for example, you might decrease until you have just a few stitches left, then cut the yarn, leaving a tail to weave in.
Circular knitting can seem a bit tricky at first, especially joining the round without twisting your stitches, but with practice, it becomes second nature. It's a versatile technique that allows you to create a wide range of seamless garments and accessories.