You can give a guild member one item per day. This will have various effects - usually modifying stats, but technically any quest result can be done. Other common things including healing and trading for currency.
Items with no use, but can be traded to shops for other items, or used in quests. They aren't strictly coins and bills - things like "stone" and "wood" could be a currency, and function the same way.
Used to increase the capabilities of the guild. This translates into sort of meta-stats, such as number of quests offered, gold discounts from shops, stat gain increases, healing rate increases, and modifying what and how many new guild members are offered for hire every day.