WATCH: Image Adjustment Options in Pixlr
Levels and Auto Levels
What are levels? Go to THIS website and read about how the levels feature works, learn what a histogram is, and other uses for the levels tool. Just read the sections that are highlighted yellow.
Watch the following tutorial about what levels are and how they can affect your photo editing. The tutorial is in photoshop but the concept is the same for Pixlr.
The concepts you just saw in the tutorial are the same in Pixlr. HERE is a screencast on how to adjust the levels in Pixlr.
Remember - levels adjusts the shadows, midtones and highlights of an image. The "Auto Levels" feature will sometimes work to change the shadows/midtones/highlights automatically, but most times doing it manually will make your image turn out better.