Originally Posted by PaperPrincess

To me applique is applying fabric (any way you want) to a background. It's a pretty broad technique, which is why it's often clarified with an adjective: Raw Edge Applique, Turned Edge Applique, fused applique etc.
I googled it and here is the definition
'ornamental needlework in which pieces of fabric are sewn or stuck onto a large piece of fabric to form pictures or patterns.'