This refers to a block of text—usually a Product Key, KMS (Key Management Service) client key, or a script—that claims to activate Microsoft Office 2016. In the piracy and crack scene, "text" often means a .txt file containing a list of stolen or generated keys.
Instead of risky bit.ly text files, consider:
Users often search for a "better" version of this text file because activation can be spotty. Unauthorized KMS servers are frequently shut down by Microsoft or suffer from downtime. Consequently, a script that worked last month might fail today. Users look for updated office2016.txt links hoping to find a script that points to a server that is currently online and responsive. However, relying on these scripts means relying on an unstable infrastructure that offers no guarantee of longevity.