To use Bitbucket, you need to install a DVCS tool on the computer where you write your code. Typically, this computer is a machine physically close to you like your home or work computer. This is your local machine or system. You also might write or deploy code to a remote machine - for example a lab computer or a server in a data center. You may also need a DVCS tool on that machine too. This tutorial refers to the typical case, your local system, but the instructions are the same for both cases.
Bitbucket supports two DVCS tools, Git and Mercurial. These tools run on all modern operating systems. For Git, Bitbucket supports 1.6.6 or later and Mercurial version 1.7 or later. Mercurial also requires (depends on) the Python programming language. The installation process takes care of making sure you get the correct version of Python.
Since you can use both Git and Mercurial on the same machine, this page shows you how to install both because you need both to complete this guide. If you already have these tools installed, skip the instructions and go to the next step in the guide.