There are several ways to install an application in Ubuntu:
You can download a source tarball (generally a
.tar.bz2file) and install it manually. (See How do I install a .tar.gz (or .tar.bz2) file?)
You can download a
.debfile and install it manually, using
dpkgor the Software Centre.
You can search for the application in the Ubuntu Software Centre and install it there, or use
aptwith the official Ubuntu repositories.
You can find a PPA or a third-party repo, and install it from there.
What are the pros and cons of each method? Please discuss security implications, frequency of updates and program reliability of each method in your answer.