A needle valve is a type of valve that is used for precise regulation of flow rates. It works by using a tapered needle-like plunger that fits into a seat to control the flow of fluid through the valve. There are a few different synonyms for needle valve, including flow control valve or throttle valve. These terms are often used interchangeably to describe the same type of valve. Other types of valves that are similar to needle valves include globe valves, ball valves, and gate valves. However, each of these valves has unique features and is better suited for certain applications. When selecting a valve, it's important to understand the application requirements and choose the valve with the appropriate characteristics.