Fusible appliqué is a glue fusible that is ironed to the back of the fabric so you can stick in onto a background fabric. There are lots different kinds. I like Wonderunder but there is Mistryfuse, Heat and Bond Lite as well as others. The main things is make sure the fusible is recommended for machine appliqué.
Regular Heat and Bond should never be used if you intend to sew over it. It will gum in your needle if you can even get the machine to sew through it. Nasty!