Gameplay changes with the server. The row of tabs names the server's gamemode, for example "Survival" or "City RP". You set the gamemode in the server's Settings, Gamemode; the dashboard suggests one from what the server reports.
Gamemode pages
Each page is a set of panels for that mode: for example money in and out, shops and auctions, jobs, teams, or match results. Panels only appear when the server sends the data they need; a panel with no data tells you which plugin or integration would fill it.
Economy
Money supply, how much the top 1% hold, and sources and sinks, where an economy plugin such as Vault or EssentialsX reports them. Amounts are in the in-game currency, not real money.
All metrics
The full catalogue for the server's game: every metric and event type with data, with a chart for each. Use it when a panel you want is not on a gamemode page.
Data sources
Which plugin feeds which panel is under Settings, Data sources. If two plugins report the same thing, choose the one to count, so totals are not doubled.