A term of endearment for a close friend, online acquaintance, etc.
Bestie, we miss you.
History and usage
The word bestie is short for "best friend." People have been using it for decades to describe those in their inner most circle or closest person to them. The nickname for best friend has shifted from bff to bestie to bsf back to bestie and was made mainstream on social media when users and creators started using it as a way to talk to their followers in a friendly way. It helps form a closer online community between the creator and brand to their audience.