BurdaStyle has a 101 on how to read sewing patterns.
From the site:
We know some people are hesitant to use patterns, but it’s really quite easy! Everything you need to know is right on the pattern, and once you start, you’ll never stop! So now that you’ve got your pattern laid out, learn what all those marks on the pattern mean. The Key to Symbols that comes in every pattern tries its best to explain, but this How To might make it even easier to understand.
To find out the basics of how to read sewing patterns, visit BurdaStyle here. – Link.