Your IRA account generally lets you invest in just about any investment; stocks, bonds, ETF's and mutual funds...very flexible. 

Your 401k or 403b employer plan will be limited-generally you'll have a menu of diverisfied mutual funds, probably 20-30 funds...pretty simple.  Many different providers administer these plans including Vanguard, T Rowe Price and Fidelity.

Morningstar has provided some model portfolio's if Fidelity administers your employer plan.