As an SP, you can supply a default URL that the end-user may see when an SSO request succeeds (that is, a session is created at your site) but the target resource is not available or not specified.
Note:

You can also specify default target SSO URLs for individual IdP connections, which take precedence over this global setting (see Configuring default target URLs).

Similarly, you can specify to prompt a default URL indicating a successful SLO to the end-user (if no other page is designated).
Note:

The error message is displayed only when the application calling the start-SSO endpoint does not explicitly provide its own error page URL. The default entry in this field is used to localize the message. For information about how to find and change the default English message and how use the PingFederate localization feature, see Localizing messages for end users. If localization is not needed, you may also specify a message directly in this field to change the default.

Your application or your partner's application may supply these URLs at runtime (see SP services), but if none is provided, PingFederate will use the default values you enter on this screen unless, in the case of SSO, a default is also defined for the connection.
Tip:

If no default targets are specified here or at the connection level (for SSO), PingFederate provides built-in landing pages for the user. These web pages are is among the templates you can modify with your own branding or other information (see Customizable user-facing screens).