Raid Chest loot - difference between 1800 and 2399? if any?

It’s not a silly question at all.

The Wanted Heroes mission reward chest is commonly referred to as a “Raid Chest,” since you have to fill it by killing heroes in raids (wars don’t fill the chest)

The little banners next to your various energy counters (world/raid/titan) look like flags, so people often refer to units of energy as “flags.”

If you’re curious about other terms, there’s a great resource that explains common ones here. That’s usually where I start if I don’t understand a term someone is using: