What does solder flux do?

Could you please elaborate on the role and purpose of solder flux in the soldering process? Specifically, I'm interested in understanding how it aids in the joining of metal surfaces. Does it remove oxides or other contaminants? Does it enhance the wettability of the solder? And how does it impact the overall strength and quality of the solder joint? Additionally, are there different types of solder flux available, and if so, how do they differ? Clarifying these points would greatly assist in my understanding of the function and importance of solder flux in electronics manufacturing.