These are things you can do besides basic ratting and mining that will bring ISK to your wallet. Some activities offer more than one type of activity, so they might appear in multiple section. For example, mission running allows you to kill NPCs, haul stuff from one place to another, or mine materials. Likewise, you can enter wormholes to mine, or rat, or kill the locals.
More Detail Here: "exploration guides", "data site scanning"
More Detail Here: "abyssal guides", "incursion guides", "mission guides", "wormhole guides"
More Detail Here: "mission guides", "wormhole guides", "mining guides"
More Detail Here: "wormhole guides"