Nowadays, we all watch movies and listen to music on our computers, instead of watching them or listening to them in our stereo or DVD players. That being said, everyone knows that they need to use a program in order to do this. There are many alternatives to do this such as Windows Media player and Winamp. My recommendation though, if you haven't heard about it yet, is VLC media player.
The main reason I prefer VLC player over anything else is because it supports all the media formats that I've come across so far. With another players, there would be usually the trouble of finding codecs and everything in order to play media. VLC producers must've been aware of the issue before creating VLC, hence you can play anything you want with no codecs or anything on it.
The next important thing (for me) is that you can sync audio/subtitles easily in the settings. There are many cases where I can't find synced subtitles for the movie I'm watching. Luckily, it only takes a minute to sync the subtitles in VLC by simply going to Tools -> Track Synchronization.
There are many other fancy options in the software which I'm not using, but some people might find use for such as recording a part of the video you're playing, slowing & speeding up, taking snapshots, a fully customizable video effects panel where you can change the graphical attributes of the media you're watching and many more. (cropping, rotating, color filters etc.) You can also download plugins for VLC media player which makes it fully customizable compared to other media players. (although there are media players which support plugins, they're usually very limited)
All in all, if you like playing media on your computer and you're looking for a software which you can use, then VLC media player is the right way to go. Even if you're not going to use its fancy options in any way, it's still the best media player out there just because of its extensive support of different file types.
If you are interested and want to try VLC media player out (it runs on all platforms too!), you can download it here.