The URL for a presentation can vary slightly depending on the account the link came from and/or how the presentation is configured.
If allowed in the presentation settings, any user with viewing permission to a piece of content will have access to the Share or Link button for that presentation in their Home tab. This allows them to gather a direct link to the content which will have a zPID (a presentation ID beginning with a 'z') near the end of the URL. This value is a unique identifier that combines the numerical PID (presentation ID) of the content and the "sender" user generating that link to share with others.
Since presentations are able to be shared by multiple users, each URL link will appear differently when compared with one another, but will still lead users to the same presentation. For example, the two links below lead to the exact same presentation, but differ slightly since they were each gathered by two different users:
VIews using these types of zPID presentation links will have additional data gathered when running a viewing report indicating who the "Sender" of the presentation was (i.e. whoever generated the link).
Presentations can also be given custom URL addresses that are meant to create a new customized link. For more information on how to create these URLs, check out this help article: Customizing your presentation URL