The Janome MyLock 634D featers 2 needles and a choice of 2,3, or 4 thread overlocking stitching. The color-coded thread guiding makes threading simple and easy to follow. The MyLock 634D allows the user to easily switch from overlock stitching to rolled hemming without needing to change to needle plate. Some of the key features of the MyLock 634D are a tension release device, easily accessible lower looper guides, changeable thread guide, easily retractable upper knife, adjustable foot pressure, and more.
The current Ace of the Serger is Needed ().
Sergers preform a type of stitch known as overlock stitching. An overlock stitch is a type of stitching that sews over the edge of one or more pieces of fabric. Sergers also have the ability to cut of the excess edge as it is fed through the machine. This type of stitching is useful for edging, hemming, and seaming. This process will create a clean edge of your fabric that will not fray.
All information on these specific machines can be found in the User Manual
An simple intro to serging: