EVE's very own crafting system.
In space.
With spreadsheets.
Almost everything in EVE, from the basic ammunition that you pew-pew with up to the enormous Titan class ships, is manufactured by players. To manufacture an item, you will need:
Blueprints come in two varieties: originals (Blueprint Originals or BPO) with unlimited runs, which as well as producing items can also be used to make copies (Blueprint Copy or BPC), which is a copy of the original blueprint with only a limited number of runs - e.g. you can manufacture 100 items and then the BPC is destroyed.
Single-run BPCs are also used for Invention, which is the only way to create blueprints for T2 (Tech II) items.
You can buy them in a lot of stations - tradehubs like Jita and Amarr have almost everything for sale - and many blueprints are put up for Contract sale, often in a bulk buy with lots of different blueprints. You can also find blueprints, including very rare ones, in exploration site loot drops.
See this page in the wiki where free BPCs are offered for newbros who want to explore manufacturing.
T2 blueprints (for building advanced items) are "invented" by using up a single-run T1 blueprint and some other specific materials. Invention is not a sure thing; there is a percentage chance that you will fail to create the T2 blueprint each time you try, although you can increase your odds by using special items.
Once you have a blueprint and some materials (usually this will be minerals which you obtain from mining, but some items such as rigs use other materials), you need to find somewhere to manufacture. Not all stations are suitable. Some have features that give you bonuses to manufacturing; some stations will let you build but not do invention. You can use the map to find stations nearby that offer the right facilities.
Do your research! Use sites like Adam4EVE to check the price of goods in Jita compared to Fountain. Make a spreadsheet of the cost of materials (you can even use macros to link a Google Docs spreadsheet to the eve-central API). Figure out what items will sell for a decent profit, but will also sell relatively quickly (use the market graph tab on the Market window to see data on daily purchases and moving average prices over time).
Doctrine ships and modules will always sell! Pick a frigate you like to fly and start building the modules, then consult the spreadsheet gods to decide whether it is wiser to buy the hull or build it. Start with maybe ten and either fly them yourself or put them on contract.
"From my experience, ships and ammo have very low (if any) profit margin if you want to manufacture them locally - let the freighter owners import them from hi-sec. There is profit to be made in building Drones and common modules (basic MWD, webs, etc.) There is a lot of profit to be made in building rigs, but it usually involves going to hi-sec to fetch the materials. Training into T2 manufacturing can be profitable, but is a long-term investment." – Shei Bushaava, Thrall Nation, Brave Collective
Manufacturing is the process by where you have a blueprint, the required materials, and a station capable of manufacturing; to create nearly any item in game. It's EVE's version of crafting, just much more of a pain than most other MMO's.