Generally speaking, the terms "soft close" and "self close" drawer glides are interchangeable. The feature stops drawers from slamming, and gently pulls drawers closed the last few inches. This pulling motion is where the "self close" term comes from.
Self close or soft close drawer glides come in side mount or undermount styles. Undermount glides look elegant, since there is no visible hardware on the drawer, and they allow drawers to be slightly wider. Side mount soft close glides are easier to install. Soft close glides may be partial or full extension.
Self close glides prevent cabinet drawers from slamming, preserving the life of the drawer and the finish on the cabinetry. This feature also minimizes the noise of slamming drawers. The self closing feature means that the drawers always will be closed neatly rather than half open.
Self close or soft close drawer glides are more expensive to install. They are a desired feature for home buyers, and add to the value of a kitchen. Some people with arthritis or other joint problems may have slightly more difficulty with soft close drawers, since they require a little extra effort to open.