That's a tough question to answer because it's really a comprehensive and globally diverse investment portfolio that invests in assets classes far beyond just the US Stock market.
Check out this blog post from Wealthfront. It does a much better job explaining than what I am incapable of.
https://blog.wealthfront.com/benchmark-diversified-portfolio/
Also a side note: Wealthfront charges a .25% annual management fee. However, for every person you invite that signs up, you get an additional $5k managed free (as does the person that signs up through the invite link). I've invited enough friends that have joined, that I still have all of my money managed free. Happy to send an invite link if you're interested