Strictly my opinion: Betterment is a company that invests your money for you and takes a small fee for doing so. They also will be doing the investing and tax loss harvesting, the only thing that is of any real value at all, and likely only for the first few years as most of their portfolio rebalancing will end up eliminating the opportunities for tax loss harvesting within a year or so anyway, and it is honestly a very small return for paying someone else to automate what is super easy to learn how to do on your own.
While they are recommended by MMM, it still isn't the best idea, but better than doing nothing or investing with a horrible company that charges you much higher fees, loaded funds, and lots of active management that means a higher churn rate - more money in their pockets, less in yours (Edward Jones, American Funds, any "investment" group that also springs from insurance origins come to mind for me anyway).
What is a MUCH better idea would be for
you to learn the basics of investing - not just so you can do it yourself, but also because you are the best manager of your money possible. No one else cares as much about your money and future than YOU. And better to pay yourself (saving the management fees) than hand over complete control of your investments to someone else. If you truly want to be successful, taking a little bit of time to figure out how something basically works is a
real investment that will pay off immeasurably for you in the end.
Index investing (which is what I believe Betterment would be doing for you anyway) is really, really easy for anyone to pick up. It can be set up with a simple handful of funds, rebalanced easily once a year (if that) and will require a minimum of effort on your part (they call many of the portfolio setups "lazy" or "couch potato" for goodness sake!).
http://jlcollinsnh.com/stock-series/^read the series and you don't need to have anyone else invest for you
https://www.bogleheads.org/wiki/Main_Page^the manifesto for any and all index fund investing (the easiest way to invest for decent returns with low fees, and requires minimal managing from you or anyone).