Go with the Vanguard 500 Index Admiral fund since tracks the SP500. Just set it and forget it even during market corrections until you retire.

There is a book you can borrow from your local library. The Little Book of Common Sense Investing by John Bogle. This book was written for beginner investors emphasizing investing in broad market exchange traded funds (ETFs) like VTI or VOO for their simplicity. Just set it and forget it. Broad market ETFs for the win. VOO is basically the ETF version of the Vanguard 500 Index Admiral fund.

Expense ratios indicate what you are paying your fund manager to maintain your investments annually. The lower the expense ration the better.