Sectors. There are a whole lot of ways to classify and categorize stocks. Sectors are just one way. You should read about sectors here and here and here. For a look at a chart with sector comparisons and comparison to the S&P 500 go here.

Books: Are there some books that you can read if you want to learn some stuff about the market. There sure are. For starters go to amazon.com and search for the term “stock market investing” and then select Kindle Edition for the book format and then select Kindle Unlimited Eligible to limit the books to ones you can read for free with the Kindle Unlimited Plan. You will get over 3,000 choices. I like to look for the ones with a lot of good reviews. If you want to know what book on investing are considered good you might want to look at the Top 100 in Best Sellers in Investing Basics at Amazon. Many of those books will be available from a library.