What is the difference between a thruster and a 2 plus 1?

Excuse me, but I'm a bit confused by your question. It seems like you're asking about two completely different concepts here: a thruster and the number "2 plus 1." Could you please clarify what you mean by "difference" in this context? A thruster, in the context of space travel or propulsion systems, is a device that produces thrust to propel an object forward. It's commonly used in spacecraft and rockets to change their velocity and direction. On the other hand, "2 plus 1" is simply an arithmetic expression that equals 3. It's a basic concept in mathematics and has no direct relation to thrusters or any other type of propulsion system. So, unless you're referring to a specific context or industry where "2 plus 1" has a specific meaning related to thrusters, I'm not sure how to answer your question. Could you please provide more context or clarify your question?