Once you understand that 3D printing builds objects layer by layer (see our explainer on how it works), the next question is: layer by layer, using what? There are several real, different technologies — here are the three you'll run into most often, with the real tradeoffs between them.
FDM (Fused Deposition Modeling) — the familiar, affordable one
FDM is what most people picture when they hear "3D printer": a spool of plastic filament (commonly PLA or ABS) is melted and extruded through a heated nozzle, tracing out each layer like a very precise, computer- controlled hot-glue gun. It's the most common, most affordable, and most beginner-friendly type — entry-level FDM printers are inexpensive enough to be a genuine hobbyist purchase. The real limitation: FDM typically leaves visible layer lines on the surface, so it's better suited to functional parts (brackets, enclosures, prototypes) than showpiece-quality finishes, and it usually needs printed support structures under any significant overhang.
SLA (Stereolithography) — fine detail via laser-cured resin
SLA printers use a focused UV laser to cure liquid photopolymer resin point by point, layer by layer, inside a tank. Because it's working with liquid resin rather than melted plastic filament, SLA can achieve much finer detail and much smoother surfaces than FDM — which is why it's the go-to choice for jewelry masters, dental models, and detailed miniatures, where a visible layer line would ruin the piece. The real tradeoffs: messier, more careful post-processing (uncured resin is a skin irritant and needs proper handling and disposal), a smaller typical build volume, and generally higher machine and material cost than FDM.
DLP (Digital Light Processing) — SLA's faster cousin
DLP also cures liquid resin with UV light, but instead of tracing each layer point-by-point with a laser, it flashes an entire layer at once using a digital projector — which makes it meaningfully faster than SLA for equivalent detail, since layer time doesn't depend on how much detail is in that layer. The tradeoff is a typically smaller build area, limited by the projector's resolution and throw.
SLS (Selective Laser Sintering) — no supports needed
SLS uses a laser to fuse fine nylon powder into a solid shape, layer by layer, inside a heated powder bed. Because the surrounding loose powder itself physically supports the part as it builds, SLS needs no separate support structures the way FDM and resin printing usually do — which makes it genuinely better for complex, interlocking, or heavily overhanging geometries that would be difficult or impossible to support otherwise. The tradeoff is a slightly grainy, matte surface texture straight off the printer, and generally higher equipment cost than FDM.
Which one is "best"?
There isn't a single winner — it depends entirely on the job. FDM for a cheap, functional, forgiving first print or a working prototype; SLA/DLP when surface detail and finish quality is the whole point; SLS when the part's shape itself is genuinely complex and removing support structures would be a nightmare. Most people's first real 3D printer is FDM, precisely because it's the cheapest and most forgiving place to start before deciding whether resin or powder printing is actually worth the extra cost and complexity for what they want to make.