The website gives an extensive look into reading a patter in chart form. It goes into all the elements of a chart, including what the symbols mean and how to go about reading it. The website also goes into how to read a chart for lace patterns, colorwork, and cables.
This website shows a chart with the different yarn sizes, also known as weights. There are various names for each size which are listed in the chart. The website also gives the needle or crochet hook size that will work best with each weight of yarn.