403B and mutual funds confuse me - Any Advice?

I was curious how your retirement plans are set up? I am just now getting started into all of this wonderful and confusing stuff, but it confuses the crap out of me. I signed up for a 2050 plan that supposedly is going to allow me to gain little bits of money without getting too involved in the mutual fund.

Is it more beneficial to invest in several individual stocks or invest in one mutual fund?

Also, if you are already retired and have invested, have you found that one is more beneficial than the other?

Thanks for any input y'all!