IFS is based on the concept that we all have several parts living within us that fulfill both healthy and unhealthy roles. Life events or trauma, however, can force us out of those healthy roles into extreme roles. These internal roles are not static and can change with time and work.

The goal of IFS therapy is to achieve balance within the internal system and to differentiate and elevate the Self  (your "true" or unconditioned self, marked by characteristics such as calm, curious, compassionate and a sense of neutral, expansive, or  peaceful body responses) so it can be an effective leader in the system. (VeryWellMD)

Somatic is a fancy word that means "relating to the body" - so Somatic IFS  integrates use of the body through breath, movement, ethical touch, resonance, and awareness of sensations, all within the IFS framework. Somatic work has been shown to be effective for chronic illness and trauma. (EmbodiedSelf)