I'm on our company's 401K plan. If you know nothing about how the stock market works, then the target date retirement fund is the way to go. The worst thing you could do is not participating in your company's 401K plan, especially if the company offers you matching dollars (Read: FREE MONEY). I started with a target date retirement fund (managed by Schwab) but almost 2 years ago, I decided to re-allocate my fund into 3 mutual funds: S&P 500, US Small-Mid Cap, and International Large Cap. I'm happy that I re-allocated my fund. Ramith Seti's "I will Teach You to be Rich" book inspired me. And, another influence that made me re-allocate my fund is the "Three-Fund Portfolio" principle by Boglehead's Guide to Investing. I don't currently have access to the funds that Bogle suggested, but if I have extra money to invest, I'd open a Roth IRA account (alongside my 401K) and do the following:

VTSMX 60% VGTSX 30% VBMFX 10%

or ETF's

VTI 60% VXUS 30% BND 10%

These allocations follow the Boglehead principle of 3-Fund portfolio / Lazy portfolio