Green tea extract shows up in an enormous number of metabolic-support supplements, and for good reason — it has one of the larger research bases of any "fat burning" ingredient.
The key active compound is EGCG (epigallocatechin gallate), a catechin with antioxidant properties. EGCG has been studied for a possible role in supporting metabolic rate, particularly when paired with caffeine — the two appear to work better together than either does alone.
SodaSlim's Green Tea Extract is standardized to 98% polyphenols and 45% EGCG, and is paired with 138mg of Caffeine Anhydrous — the combination the research base is actually built around, rather than green tea extract alone.