Chapter 1 needs to do three things, preferably concisely:

  1. Introduce the protagonist. This includes:

    1. Their status: What is their role in society? Their profession, their approximate age, etc.

    2. Their personality: Perhaps the most important part.

    3. Their relationships: No person exists in a vacuum. They should have some friends, acquaintances, rivals, and/or enemies.

  2. Introduce the setting. If it's the real world all you need to do for this is make that clear. If not, you must introduce your world:

    1. Physically: Is it basically set on Earth, just not the real (modern) Earth? Is it a flat world with no apparent end, the surface covered with ocean and a few massive pillars of land that people live on (like one I've created)?

    2. Culturally: what people believe is most important - what are their values? Do they have a religion(s)? What kind of government do they have (or do they)?

    3. Its rules: Readers need to know the technology level, whether there's magic, and if so how it works, very early on so they know what is and isn't possible in this world. This is probably the worst area to mess up in.

  3. Introduce the plot. It doesn't have to start it directly, but it should at least include a plot hook that shows how it's going to get started.