Since curse does a bad job explaining this:
Download the curse client here and then search for Minecolonies Testpack there.
Downloading it on this page will give you a .zip that will bring you nowhere.
Minecolonies is a SSP and SMP town building mod, allowing you to create your own thriving Colony within Minecraft.
Featuring many NPC workers, ranging from Builders, Crafters and Farmers, to Guards, Enchanters and Alchemists, the mod provides the ability to create a unique Colony with many many inhabitants.
A robust permissions system in the SMP version allows you to collaborate on a single colony with your friends, or have individual colonies each competing to be the best!
Featuring completely free placement of structures within your Colonies boundary using our fantastic build tool, allows you to visualise a buildings position before placement, ensuring you can build increadibly large and detialed Colonies that look fantastic.
This modpack allows you to test out the mod in it's always latest version with some extra mods you already learned to love.