Here's a breakdown:
* It often denotes a person who adheres to a particular ideology, belief system, or artistic style.
* Examples: *communist*, *feminist*, *realist*, *impressionist*.
* It can also denote a person who specializes in a particular field or activity.
* Examples: *linguist*, *scientist*, *artist*, *pianist*.
The specific meaning of "-ist" can vary slightly depending on the context. However, it generally points to someone who is identified with or dedicated to a specific set of ideas or practices.