Dacron or Batting is a polyester batting that should be added to any foam surface so that it will not be exposed directly to the fabric. Dacron has many indispensable qualities.
First, batting reduces the friction foam has, and thus reduces wear to fabric. Most importantly, batting fills in any slackness in how you’ve upholstered your furniture, cushion, etc. And because this will make your upholstered piece looks better.