Collaboration on social media involves two or more businesses/social profiles aligning to work together on a single project or initiative.
Collaboration can take many forms, from simply tagging another business or profile in your social posts to allowing celebrities or influencers to log into your account(s) and record a live video and/or answer user questions. This strategy connects you to another business/profile in the virtual space, representing a social-media-focused form of co-branding.
Collaboration is a powerful tool for attracting new followers and for establishing credibility and visibility in your space. Your company can quickly reach a new, potentially massive audience by collaborating with larger or more targeted and integrated voices online. As with co-branding, however, the alliance must be strategic, and it must be well-thought for maximum effectiveness.
References
https://sproutsocial.com/insights/social-media-collaboration/