What is the word used to describe the Product name that has become synonymous for the product itself?

Eponyms

When we say we used Scotch Tape instead of saying we used cellophane tape, the product trade name Scotch Tape has been genericized. It has been established as the generic name for an entire line of products regardless of who makes them. There are many examples such as Skilsaw is a circular saw, Kleenex is tissues, etc.