Sorry. Let me explain it this way. When you use the brush tool in LR you are "Painting" on your image to mark the area on the image where you want some change to be made. The actual changes to be made in that area is called the "Adjustment", and the area where you painted is called the "adjustment mask." The adjustment (actual changes) which are applied to that area is defined by where you move adjustment sliders such as Contrast, Exposure, White Balance, Saturation or several others in the panel of sliders that displays when using a brush (looks a lot like the basic panel). Each of these sliders can be moved either left or right by any amount desired. The combination of those slider positions are considered the full adjustment. In my prior post I was using as an example that you had moved the Exposure slider +1 stop. However, that was just an example and in fact the "adjustment" could be the change of any combination of sliders in any amounts. For example, I could have decided to set the exposure slider to +2, the Contrast slider to 20 and the saturation slider to 16.
While you are brushing (that is painting with your mouse to create the mask) the Flow slider controls the strength of the mask that is created each time you brush over an area. If the Flow is set to 100, then you get 100% of whatever the adjustment is by brushing over an area of the image one time. In other words you get the entire effect of the adjustment slider positions. So, as an example, if your "adjustment" was that the Exposure Slider was set to +1 (ie 1 stop brighter), then wherever you brush will get 1 stop brighter. If you change the Exposure slider for that adjustment to +2, then those areas of the image will become 2 stops brighter. Or if you move any of the other adjustment sliders you will get 100% of the effect for where ever you moved the sliders too.
However, had we set the Flow to 25 instead of 100, then every brush stroke would only add 25% of wherever we placed the adjustment sliders. So, going back to our example of setting the Exposure Adjustment slider to +1 stop, if we brush over an area of the image with the flow set to 25, we would get a 1/4 stop brightness increase. If we brushed over that same spot a second time, then we'd have 1/2 stop increase in exposure. If we brushed 3 times we'd have a 3/4 stop increase and we'd have to brush over that same area 4 times to get the full 1 stop increase. In other words, with the Flow slider set to 25, we get 25% of whatever the adjustment slider positions are with each brush stroke. If we set the Flow to 20, then each brush stroke would add another 20% of whatever the adjustment sliders were set to.
To say this another, slightly more technical way, as we brush with the mouse, LR is creating another layer over the image called a mask. But rather than having colors on this layer that you will see in the image, each pixel position has a value between 0 and 100. This number represents what percentage of the changes made to the adjustment sliders to apply to that pixel position in the image. If you haven't brushed at all yet, all those mask numbers are 0 meaning that none of the adjustment slider changes should be applied to the image pixels. If those mask numbers are 100 then 100% of the changes to the adjustment slider positions are applied to the corresponding pixel positions. If those mask numbers are, say, 50 then only 50% of the changes to the adjustment slider positions will be applied to the corresponding pixel positions. Each time you do a brush stroke, the value of the "Flow" slider gets added to any number currently in the mask at the positions brushed over. When you turn on the Mask Overlay so that you can see the mask itself (usually in pink) the density of the pink is based on these numbers. If the mask numbers are low (due to a low Flow Slider setting) the pink will be very faint. If the mask numbers are high, like 100, then the pink of the mask will be a much deeper (less transparent) pink.
The Density slider acts like a cap on how much affect can be applied to any area being brushed. Normally this is left at 100 meaning that you can get the full effect of any adjustment you make. However, if you set this to 50 no matter what your flow is or how many times you brush over the same area, the maximum affect will be only 50% of where ever you had moved the adjustment sliders to. Personally, I have yet to stumble on a situation where this limit or cap was something that I needed to use. Perhaps someone else on this forum can describe such a scenario.
If this is still too complex (probably because I'm not explaining it well), you will probably do just fine by leaving the Flow slider set to 100 and the density slider also set to 100.
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