If you're coming from a linux environment, you're probably used to having Apt or Yum available. OSX has no built in package manager so you've either got go out and find compiled binaries somewhere or install from source, both of which are tedious and searching the web for it is time consuming vs. the `brew install wget` commands that you can probably guess and it'll take care of installation in the background while you do something else.
No, Yum isn't available or compatible, it's coupled to Red Hat/Fedora/CentOS linux distributions like Apt is coupled to Debian/Ubuntu/Mint distributions.
Homebrew/MacPorts/Fink are nearly the same thing, they just don't come installed by default on OSX.
See here for stuff you can install with one command: https://github.com/mxcl/homebrew/tree/master/Library/Formula...