From Nookipedia, the Animal Crossing wiki
The Bell (ベル, Beru) is the main form of currency used in the Animal Crossing series. It is used primarily to buy things from Nook's and Crazy Redd's as well as from the villagers, Gracie, the Able Sisters, Brewster, and Harriet. In the original Animal Crossing, players can carry up to 849,999 Bells at any one time. In Animal Crossing: Wild World and Animal Crossing: City Folk, this is substantially expanded upon as players can have 99,999 Bells in their wallet and fifteen 99,000 Bell bags in their pockets, bringing the grand total to a maximum of 1,584,999 Bells on hand at any one time. In Animal Crossing: New Leaf, players can carry sixteen 99,000 Bell bags in their pockets at one time, for a grand total of 1,683,999 Bells at once. This can be further expanded by putting Bells into letters for an additional 990,000 Bells, but these do not count as on hand as they will not be counted when the player talks to someone who wants to sell something.
Bells are most often seen in tan sacks with a dark brown star in the middle, tied with red rope at the top but are actually coins if viewed as items in quantities of multiples of 100 (as opposed to 1,000 as is normal) in City Folk. In Animal Crossing, all money appears in a sack.
There are many ways to make Bells; the player can sell items and fruit, do favors for villagers, sell valuable fish and bugs, or even shake trees to get out money. The player can also make a Money Tree by burying Bells with a golden shovel. Money trees will not always grow, but they can be profitable.
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