Fluid level sounds low. There is a sensor in the maser cylinder that registers the level. If it is low, on braking or acceleration it moves and the sensors drops just enough for the light to come on.
It is an indicator that you do need brakes as well. Why? The fluid is low for a reason. In most cases, the pads/shoes wear and the fluid fills the piston void at the brakes, as it fills to replace the amount of pad/shoe that is worn the level drops within the Master Cylinder.
But in any case, I am sure you will find your fluid level is low. Top it off and your light issue will be solved.
