Your insurance provider can dive into greater detail, but here are a few additional points to consider:

Some insurers require comprehensive and/or collision coverage before they'll add this coverage to your policy.
As with most insurance coverages, you'll find there are limits, whether it's a cap on the cost of each incident or a limit on the number of claims you can file each year.
Coverage typically only applies to the car your insurance company insures; it doesn't follow you, for instance, when you get behind the wheel of a friend's car.

Of course, nothing beats regular car maintenance and seasonal driving precautions to make sure you don't end up stranded along the side of the road in the first place. However, it can offer comfort to know that if you purchase this coverage, you may be eligible for reimbursement for expenses incurred when you are in need of help.