3D printing is a modern rapid prototyping technique in which a solid object is created through a layered deposition process. 3D printing is referred to as an "additive manufacturing" technique, as instead of taking material away from a stock piece in order to create a desired object, such as in milling or turning manufacturing techniques, the material for the object is added by the printing process. 3D printing techniques make it very simple to quickly create both complex and simple objects.
The 3D printers available in the MakerSpace are all Fused Filament Fabrication (FFF) printers, meaning that to create the desired part, molten polymer (melted plastic) is "extruded" into a filament, which is deposited in the desired shape. The hot plastic fuses with previously deposited layers, creating the desired part. Due to the nature of molten plastic, FFF 3d printed parts have a degree of "slop" that is difficult to eliminate, so a different manufacturing technique, such as laser cutting or CNC milling, is likely necessary for parts that require very high degrees of accuracy.
The Tulane MakerSpace contains Ultimaker 2 and LulzBot TAZ 5 3d printers with heated beds to allow for both ABS and PLA printer filament. ABS filament allows for better finishing effects (such as smoothing), but PLA provides a more rigid part and has has much better adherence to the print bed. There are other advantages and disadvantages to both. Cost is the same (currently ~$18 per kg).
While ABS and PLA are the most commonly used filaments, many other products exist with special qualities (flexible) or appearance (wood, ceramic). There is a good summary and comparison at  MakerSpace users wishing to try out these filaments should procure them and work with a ninja to load them onto the printer.
The standard slicing software favored for these printers is Cura, which allows you to arrange and size your model and set options for the printer to follow. The LulzBot version of Cura is recommended, as it contains more features, and works with both the TAZ 5's and the Ultimaker 2: https://www.lulzbot.com/cura