Types of 3D Printing
Every 3D printer belongs to a process family, and the family decides more about your results than the brand on the front does. It sets what materials you can run, how much detail you get, whether parts come out strong enough to use, and how much cleanup sits between the print finishing and the part being usable. Pick the family first, then shop inside it. Below are the six families covered on this site, what each one is genuinely good at, and where each one frustrates people.
Material Extrusion
Melts thermoplastic filament and lays it down in layers. This is what almost everyone means by a 3D printer, and it is the cheapest family to buy into and to run.
VAT Polymerization
Cures liquid resin with light, one thin layer at a time. Detail and surface finish are in a different class to filament printing.
Powder Bed Fusion (Polymers)
Fuses nylon powder with a laser. The surrounding powder holds the part up, so there are no support structures to remove.
Material Jetting
Jets droplets of material and cures them as it goes, more like an inkjet printer than a filament machine.
Binder Jetting
Deposits a liquid binder into a powder bed to glue each layer together. No heat is used during the build itself.
Powder Bed Fusion (Metals)
Melts metal powder with a laser or an electron beam to build fully dense metal parts.
If you are buying your first machine, the honest short answer is that material extrusion or vat polymerization is almost certainly your family, and the choice between them comes down to whether you care more about part strength or surface detail. The other four families are worth understanding so you know what you are not buying, and so you can read spec sheets without being sold a process you do not need. Start with material extrusion if you want a working part, or vat polymerization if you want a beautiful one. When you are ready to compare actual machines, go to the best 3D printers under $300 or browse the printer reviews.