Metering is how your camera measures the amount of light in the scene and recommends and/or sets the exposure level of a photo. It's about brightness.

Autofocusing is how your camera measures the distance between the camera and the subject appearing in the area of the frame That you've indicated you want it to focus upon (or the area of the frame it guesses you want to focus on if you allow it to automatically select the AF point). It's about setting the lens' focus distance.

With many advanced cameras, several different metering modes are offered. Which works best for a specific situation is dependent upon the particulars of that situation. For example, taking photos in a dark theater with a few brightly lit actors in only parts of the scene requires a different metering strategy than taking landscape photos with a very bright sky and a less bright landscape.

Likewise, many advanced cameras offer several different ways of telling the camera what should be focused upon. Which works best depends on the situation. Taking a still life photo from a tripod mounted camera has different AF requirements than tracking a running athlete during a multi-frame burst.

Some cameras even link the metering system and the AF system in certain ways. For example, they might heavily weight the metering in the area of the frame that is selected as the AF point and place less importance on the other areas of the frame.

But I am wondering about are they on at the same time?

They can be, and most often are. But advanced cameras can be set up to control each using different controls so that metering and autofocus can be done independently of one another. Again, the situation in which one is shooting will, to a large part, determine when this is optimal and when it is not.

That is what I am confused about which one is on and how to turn them on and off or are they all on at the same time.

Which is on or off, and when, depends on what settings you have selected. Your Sony α6300 Manual should be very helpful in explaining which settings do what.