What is Infusion Vinyl Ester?

[76SeaRay]

Looking at ordering 5 gallons of resin. Planning to use epoxy for the bedding and covering the stringers and Polyester for the decking but considering Vinyl Ester. When I checked pricing I ran across Infusion and Laminating Vinyl Ester. What is Infusion and how is it used? It seems a lot less expensive.

Thanks...