Also, say you have an account that has 5% interest rate and you have say, $5,000 in it. Does that mean that by year end, you should have $5,250? Is that how it works?
The APY (Annual Percentage Yield) is the number you want to look at. If the APY is 5.00%, then yeah, you'd have $5,250 at the end of the year. But then if that CD isn't in an IRA or 401(k), you're taxed on that $250 interest, so you only get to keep $212.50 (assuming 15% tax).
Say you make $50,000/year, and start to save 10% of that. If you keep that 10% under your mattress as you're saving it, then use it to get a $5,000, 5% APY CD at the end of year 1, your total savings at the end of year 2 will be $10,212.50 ($10,000 saved + $250 interest - $37.50 tax)
On the other hand, let's look at a 401(k). In that case, 10% gets deducted from your (monthly) paycheck and immediately invested in a fund earning the same 5% APY. Your employer matches 50% of your contribution, up to 6% of your income. So in a year, your total contribution is $6500 ($5000 from you, $1500 from your employer). At the end of year 2, $13,000 has been put in the account, and it's earned $669 in interest (which is not taxed) for a total of $13,669.
But wait, there's more! The $10,000 you contribute to your 401(k) reduces your taxable income by the same amount, so you pay less income tax. Again assuming 15% tax, that's another $1500 saved. We'll even assume that you just keep that extra money under your mattress, and still your total saved by the end of year 2 is $15,169 ($13,699 + $1500).
$15,169 vs. $10,212.50. Damn.
That's almost $2,500/year in free money that you'd be throwing away by not investing in a 401(k). And that differential only grows bigger as the years go on.
Ok, class dismissed!
Neil