So let's go over what these 3 tools are and how they can best be used.
Brightness/Contrast: The technical definition of these in graphic design are- brightness raises or lowers the entire curve with respect to light output and contrast is the ratio of luminance between the brightest white that can be produced and the darkest black that can be produced. [source] These two are often grouped together in a software. They are actually NOT always the best features to use if you want an image to look better/clearer/etc (especially turning up Brightness). The major downside is not much fine tuning availabilities and therefore looking particularly grainy or washed out. I do recommend using it when you want to wipe through the entire image, for example in this other tutorial that I made to clear out particular spots in an image. See below to see where you can find this tool.
Color Balance: This is a tool where you can use sliders to adjust the RGB filters of an entire image, as well as the highlights, midtones, and shadows of each filter. If you follow basic color theory, this is much better for fine tuning the amount of primary colors throughout the image. For example, if you have an image that is too dark, you can increase the warmer colors in the highlights, like red, to brighten it, and if you have an image with unflattering yellow hues, you can decrease the greens in the midtones and increase the blues. See below to see where you can find this tool.
Levels: "Levels is a tool in image editing programs which can move and stretch... brightness, contrast, and tonal range by specifying the location of complete black, complete white, and midtones in a histogram."[source] That blog goes wonderfully in depth on its underlying functionality. This other blog gives a great summary on each option in the levels dialog box. In summary for the everyday user though: (a) move the points on the histogram's curve to adjust the amount of darks & highlights for all the pixels throughout the image, (b) move the black, white, and grey sliders to determine more or less of each option, (c) move the input/output levels to shift where along the RGB values spectrum will be displayed. See below for a breakdown of this tool.
Although these are fairly basic, I hope you still found both of my tutorials helpful in some way. Happy editing!