One of the biggest financial mistakes many people make is NOT taking advantage of a 401K plan.
Everyone's plan is a little different but basically here's how it works...
It's pre-tax, so that means the money is deducted from his gross pay (the amount before payroll taxes are deducted). So if hubby makes $800 a week, and he elects to have $50 a week put into 401k, the taxes will be based upon $750. You will need to pay taxes when you withdraw the money from the account.
In most cases your employer will match up to a certain amount. So if hubby chooses to put in $50 a week, his employer will put in $50, so you'll actually be investing $100 a week.
Hubby gets to choose what type of investments (stocks, bonds, money market) he would like to invest in. Many plans have a default where you can let the investment manager (that's NOT his employer, it's the company that is managing the funds) choose for you.
As with all investments, there are risks involved, so there is a chance you can loose money. Typically you'll get a statement every 3 months to let you know how your account is doing. Most companies also have on-line access so you can check it as often as you wish. Remember that this is saving for retirement, so you need to focus on the long term.
Even though this is your money, you will not have access to it. It's not like a savings account where you can withdraw it at any time. There are certain rules for withdrawing, some are set by the IRS and others are set by the retirment plan. If some major unseen financial event occurs, (often called a hardship), such as a major illness, you may be able to withdraw the funds, or borrow from it. If you take out money before retirement age, not only will you have to pay the taxes, but you will also have to pay a penalty. Remember, the point is to save for your retirement.
Now after learning all that, it seems like it might be a bad idea. It's not. You should invest. It's one of the best financial decissions you can make.