What are algin and carrageen ?

Are they algae or are they hydrocolloidal byproducts of red algae and brown algae respectively ?

Algin is a type of polysaccharide usually found in the cell walls of brown algae. It forms a viscous gum like substance when mixed with water. It is widely used for thickening of ice creams, cosmetic, pharmaceuticals etc.

Carrageenan is a type of sulfated polysaccharide which is extracted from red seaweeds. This substance is extensively used in food industries gelling, thickening and stabilizing food items. It works as an alternate of gelatin.