The abbreviations are what kefo said but i also thought it would be helpful to explain them since you said you didn't understand
Million combined stats: similar to kcs or bcs, they are how people discuss stats on profile or stat items in your showcase
Notifications: All notifications in your notification section, but (as kefo said) people often use this when talking about battle notifs
In house seller: A cat seller who regularly sells their cats to a specific cat club so they are able to have people pay in bentos directly to the admins instead of finding their own cat seller. This person sometimes stays in club, sometimes doesn't.
Strip-farm war: Typically when two people or two groups of people are hitting each other and hiring the other's tutors. When a player has more money out, it causes them to lose more money.
Drop volley profit: The process of hiring a tutor back and forth in order for one person (or both if there is a third party involved) to make money via the profit from the tutor hires. Then one person keeps / drops the tutor.
Question answered, so I'll be locking the thread
