Using the in-game character creator it's up to you to create your own unique Sims and take control of their lives as you play the story elements of the game. This will include building houses for them, starting families, socialising with other Sims to form relationships, and finding them a job so they can earn money.
Money is in the form of Simoleons and SimCash and these currencies can be earned through in-game quests and micro-transactions. It can be used to either purschase items such as clothing and furniture or more importantly to replenish the energy of your Sims. Energy is used to perform the actions of your Sims and this will slowly decrease while they are awake. If a Sims energy runs out they will collapse from exhaustion and fall asleep on the floor.