Cura is a slicing software that sets the options for a 3d printer to follow and then creates detailed instructions for the printer by creating a g-code file. This file can be saved to an SD card and transferred to the printer.
Cura allows you to arrange, orient, and re-size your design file before printing. It also has option to automatically calculate things such as the top- and bottom-layer thickness and how much in-fill your printed object needs.
Note that Cura is not software that can be used to design a model, it is basically a program that takes a final design and translates it into the printer's language.
Cura is open source software. Anyone can download and install it for free on their personal computer. We recommend the version distributed by Lulzbot, maker of the Taz 3-d printer. It works with both the Taz and our Ultimaker 2, and is available in Windows, Mac, and Linux.
Install Link: https://www.lulzbot.com/cura
For more information on Cura, please see this downloadable pdf from Lulzbot