Valor is the points that are given for the Clan War system, while silver is the spendable currency reward for completing specific Clan tasks. Each task will list the specific reward. Each Clan member earns their own Valor and Silver from doing tasks. The total amount of Valor is added to the entire Clan for War ranking purposes.
Silver is used in the Clan store to purchase Gadgets, Modules or Clan Chests with various rewards. It can be earned from completing Clan tasks during the War or be bought in the Black Market.
Silver Boosters can be purchased from the Clan Store for Gems. They double any Silver earned from completing Clan tasks or collecting Income for a set number of hours. Silver Boosters apply only for a player who activates them unless purchased and sent as a gift to someone else in your Clan.