The answer to this question varies from tablet to tablet. Some devices, such as the Nexus 7, come with the user manual on the device accessible through Play Books. Others have their user manuals available online. Try entering "[Your Tablet Model] user manual" into your favorite search engine.
Much of the user experience for Android devices depends on the operating system version installed on it. On your tablet, try going to Settings then About to find which version of Android you are currently using. From there, you can search on the Google Play Store for the Quick Start Guide for that particular version of Android.