Workshops are friendly settlements that you can personally manage, making it a mini-game on its own. Established workshops can produce caps and consumables over time. Workshops can also be linked via Supply Lines which will allow them to share their resources. With established workshops under your management, you won't have to worry about income that much.
The first workshop you'll get is Sanctuary. Upon unlocking this feature, you can scrap various objects within the workshop's territory or store them so you can use them later on. You can also freely move or relocate movable objects, build new ones, or even build new structures and buildings from scratch. These objects and structures require the same crafting materials you can use for upgrading your armors, weapons, and Power Armors. That said, collecting loot in Fallout 4 just became a very integral part of the game.
Workshops have several stats to consider:
People: These are your settlement's population. The more people in your settlement, the larger it grows. This will allow you to build more structures. Remember that as your workshop grows, so as their needs like Food, Water, Beds, and defenses.
Food: Food is basically the crops you plant in your workshop. Most plants can only be planted on dirt. You don't have to worry about their growth or watering them. Just assign a settler to tend to them and they'll start producing foods.
Water: These are the source of fresh, clean water for your settlers. The water need of your workshop will depend on its population.
Power: This is a non-essential feature of a workshop. A settlement can function without power but you can't run a recruitment beacon or enable some traps without it.
Defense: This is the overall rating of how well your settlers can defend against attacks. You can build automated turrets and traps to increase your workshop's defense rating on top of building watchtowers and assigning guards to them.
Beds: One bed is assigned to one settler. Your workshop can have more settlers than beds but their overall happiness may get affected. Beds are cheap to build anyway.
Happiness: This is the settler's overall morale. You can further increase this by making fancy homes and buildings and adding decorations. However, these are non-essential early so don't bother aiming for a 100% happiness until you're late in the game.
Size: This determines the limit on how many structures you can build at a time. Make sure to scrap all unnecessary items in the area to make room to your essential structures.