They seem to offer peace of mind, but I had many questions about them. And I was surprised by the answers.

What’s an extended warranty?
A warranty is a company’s promise to stand behind its product. Most products come with a free manufacturer warranty, so, for example, if your toaster breaks within the warranty period (often a year or two) the maker should repair or replace it. Extended warranties provide similar guarantees for additional years. But they may have different terms than original warranties and are often sold by other companies.

Why are they everywhere?
Simple: They’re a huge moneymaker. According to the nonprofit Consumers’ Checkbook, stores typically pocket 50 to 70 percent of the cost of warranties. They’re that profitable because buyers overestimate the chances a product will break during the coverage period, according to a University of Pennsylvania Wharton School of business study.

Are there any alternatives?
Most major card issuers provide free extended warranties for purchases made with at least some of their cards; check your card agreement for details, especially exclusions. Another way to get a free extended warranty is to shop at Costco, which provides extra protection on TVs, computers, appliances and some other products.

How do I assess whether to buy one?
First, don’t rely on a salesperson’s description. Ask for a copy of the policy and study it carefully, along with the manufacturer’s warranty and your credit card’s protection plan. Look for duplicate coverage, exclusions, deductibles and claim requirements such as having to ship the product to a repair shop. If you can’t be bothered or the fine print is too confusing, think twice. USA Today tech columnist Kim Komando advises that rather than spend money on a warranty, you should apply those dollars to a more reliable brand or buy protective cases for your goods and treat them right.

But shouldn’t I get one for my new car?
Maybe, if you’re buying a model that’s unreliable or expensive to repair. But you’re better off checking reliability ratings and avoiding vehicles that will drown you in repair bills, according to Consumer Reports. And don’t let any sneaky salesperson add an extended warranty onto your bill without your OK.

Any last red flags?
If the warranty is being marketed by aggressive telemarketers or via texts or emails, steer clear. Many of these warranty offers are just “flat-out scams,” reports the Michigan attorney general’s office.

As for me, I’ve decided to skip all extended warranties. I can live with a little risk.