WiFi File Explorer has but one purpose: lets you access the files on your Android device via any web browser on the same network. Generally, this means a PC through the same WiFi network.
This can be used for both upload and download files, and it's much faster than using other methods such as Dropbox. The only thing faster is probably USB cord but that's so inconvenient.
To use this app, just run the app, and when it's active, it gives you an URL, which you can go to the PC, type that into whatever web browser you use, and voila, you are in your phone's directory structure through the web browser. Upload, download, browse, view, do anything you like. It is that simple.
And right now, it's less than a dollar. Trust me, this app is great. Pay for it. Though there's a free version for you to try as well. It's limited though.