I accidentally gave Plot[] an equation as an argument. It returned a plot instead of an error. Can someone tell me how Plot[] interpreted the argument to arrive at the plot it returned?
It plotted f(x)=x^2 - 2. I think this is a normal behavior, that is expected when someone wants to plot the solutions of an equation.
Interesting! How about this:
Plot[x^2 == 2 x, {x, -3, 3}]
It would seem that Plot[a == b,...] is evaluated as if it were Plot[Subtract[a, b],...]. This way you can visualize the solutions of a==b as the intersections of the plot with the x-axis. This is the only justification that comes to mind.