Mechanic's and engineer's communicate using specialized words and phrases. Many of those words describe features and structures of parts. These are called "Geometric Terms". Mechanic's Toolbox software defines many of those "geometric" terms with pictures and description.
Hint: Experts in any field judge younger members of their profession by their use of specialized terminology. Incorrect usage is a "give-a-way" that you lack experience. Learn the language of your profession is an important part of becoming known as an expert.