Maybe I don't know what I mean, either!
Just saying it definitely changes the color output toward some standard that I (perhaps incorrectly) thought was RGB. It's not only brightness and contrast.
Ah, "RGB" and "sRGB" are different things! "RGB" is, well, the "big picture" of R, G and B values that make up an image pixel or range of pixels, but those values are then translated into the "color space" of an image which could be sRGB, AdobeRGB, ProPhotoRGB, etc.
So, "sRGB" is a color space in which the RGB values for a particular "tone" are defined/translated.
When it comes to a monitor, it's true that many monitors, in fact most monitors, come quite close to "matching" the sRGB color space, and also many if not most image viewers and browsers only work "well" with images that are "translated" to the sRGB color space. So actually for "generic work" your monitor and software could use sRGB as a "working color space/profile", that may in fact be in the the "built-in" monitor profile that your system uses. But when you calibrate, the calibration process does a more accurate/"exacting" process of measuring your colors and then developing a profile that (we hope) will be accurate in porcessing those colors, giving "instructions" to your graphics system, and then producing an output that will help you to get prints that will "rock"!