Training optional, but you must feel confident in the use of the device and must have read the equipment instructions.
A Dremel tool is essentially a handheld rotary tool. With a variety of attachments available, a Dremel can be used on materials such as glass, wood, metal, plastic, and more for all kinds of tasks. In other words, this is one tool that with a simple switch in attachments or accessories can turn into many tools all in one.
How to get started and loads of videos with suggested ideas: https://www.dremel.com/gb/en/make-with-dremel/how-to
An overview of the Dremel head accessories: https://www.youtube.com/watch?v=fWyZqLSnLX4