This is a Wax Stamp, which may also be referred to as a Wax Seal Stamp or Stamper. They come in many different colors, materials, shapes and sizes. A 'Wax Stamp' is exactly that, it is a stamp that is used to create an impression into wax. The end result is known simply as a Wax Seal.
This is a Wax Seal, which is what you end up with once you press the stamp into the melted wax. They may also come in many different colors, shapes and sizes. The reason they are referred to as 'seals' is because for centuries they have been commonly used to seal envelopes or a piece of written correspondence.
In today's modern age Wax Seals can be used for other purposes such as an embellishment for your branding / packaging or even wedding invites.
A Wax Stamp is a great way to experience the ancient art of wax sealing for yourself, and is recommended for anybody who enjoys the process of creating their own wax seals by hand. Pre-made wax seals or 'Self Adhesive Wax Seals' can also be a practical alternative for those who simply don't have the time to create their own. The only drawback with this method is that you don't get to experience the feeling of pride and satisfaction that you would normally get from creating your own.