mrd is correct in how a Equity Line of Credit works (at least here in Alabama). Example: You may have a credit limit of $10,000 but have only used $2,000 and that is all that your payment will be based on (the amount you have used). That money can be used for anything at your discretion: buying a car, vacations, college tuition, Christmas shopping, groceries, medical bills, etc. If I'm not mistaken, the interest you pay each year will also be tax deductible.
Keep in mind tho that it is a lien against your home. If you should ever refinance your home or sell it-that lien will have to be paid off and closed.