Let’s say that you’re working on a plugin that has its own plugin settings page, and on that page there are options to determine what type of posts will support part of the functionality of the plugin.
For example, let’s say this plugin will be introducing a meta box for each post type that extends the type of information that the user can add to a post. The settings page allows you to control which post types will offer this information.
To give a concrete example, take a look at the following screenshot:

Granted, it’s a small example but it makes the point: We have a plugin settings page that displays all of the post types that are in the current theme installation. If selected, we’ll save the values to an options array.
When it comes time to read the values, there are a couple of ways to go about doing it, but one that’s arguably simpler than all of the rest.

