The difference between 401k and IRA plans are both small and large. You'll find many small details that differ between the two, but for the most part, you can break it down to one main thing, your level of control.

401K plans are employer sponsored, which means you sign up for the plan through your employer and your account is handled through them. You are typically offered a few choice plans on how you will invest your money, which does take some of the control out of your investments, but some people like how this simplifies the process for them. The biggest advantage of one of these plans is that many employers will offer you a company match up to a certain percentage. So, for instance, if your company will match you up to 2%, then when you invest 2% of your income they will match that amount. This gives you more than just the money they match directly, this also gives you more money to invest and grow towards retirement, which can be a great help.

IRA, or, independent retirement accounts, are much more self directed. You go out on your own and find a company that you would like to handle your account, and you make all the decisions about how the account will be handled. While with an employer sponsored plan you are offered several plans to choose from that will decide how your savings are invested, with an independent retirement account you make all the individual decisions about how your money will be invested. You also always have the option to set up a traditional or Roth account, traditional accounts are before taxes (which means you will pay the taxes when you withdraw the funds in retirement) while Roth accounts are after taxes (which means you withdraw tax free in retirement).

So, basically, broken down, the main difference between 401k and IRA savings plans is the level of control you have, and of course, the employer match.