Use of apps and cost

As the other poster mentioned, be sure to read the entire description. Also, when browsing the App Store, some apps will be labeled with “In-App Purchases.” This does not necessarily mean that you must buy something to use the app but it does indicate that there will be purchases available in the app. You can scroll to near the bottom of the app description and click to look at the listed In-App Purchase options before downloading the app.

You have to be sure to read the full description of any app before downloading. Many are only "free"for a limited time. After that, you must pay for it.