Answer:
1. x represents where you start on the graph of the x-axis and that is why m is in front of it. M is the slope. so y technically doesn't equal both of them.
2. the slopes intercept is represented by b. the slope intercept is where you start on the y-axis of the graph.
3. the m in y=mx+b represents the slope which is followed by x so you can start graphing on the x-axis.
4. as said in answer 2, b is the y-intersept, which if you have in a equation means where you start on the y-axis
If you have any more questions feel free to ask in the comments or whatever they are called. I hope this helped.