Every time you raid a village, the same amount as what you looted appears in the Season Bank. At the end of the season, you get the resources in the Season Bank for yourself.
With Gold Pass you can upgrade its capacity to the maximum of 25 Million Gold and Elixir, and 250k Dark Elixir.
Without Gold Pass, Season Bank is limited to 5 Million Gold, 5 Million Elixir and 50k Dark Elixir.
How to fill up your Season Bank: