Answer:
M is the slope of the equation and basically the constant rate of change. So when there are two given points, the slope of the line between them will equal m.
B is the y-intercept. The "starting point" on the y-axis.
Y is the dependant variable and the unknown that the equation solves for.
X is the independant variable, the input.
To plot an equation, plug in random x values which solves for y. After plotting 2 or more points, you can simply connect them with a line. If it's not a straight line, some of your points are wrong.