Your device may not have enough storage space to hold all your files you need, or maybe you just like to stream movies or music stored on your computer to your phone, or you can just see your documents you just updated on your computer in your android device. Then here is how you can do it, what you will need is a computer connected to LAN network and android device connected to same network over WiFi.
Download and install this File manager app from Google Play store on your android device.
And now check your computer's IP, read HOW TO KNOW YOUR COMPUTER IP?[WINDOWS]
Now as you know your computer IP, note it down.
Now, open your Control Panel and then Network and Sharing center
After that, from left side of the window, click on HomeGroup
N0w open click on Change advanced sharing settings.
New window will appear, now from All Networks check " Turn on sharing so anyone with network access can read and write files in the Public folder", it must be enabled. Turn off password protected sharing if you want to access files without any password, if you don't turn it off, then you will have to enter the username and password that you have in your computer.
And save the settings and close it.
Now a new menu will appear asking for these details.
And if you not Turn off password protected sharing, disable anonymous login and enter your computer username and password and save it.
Select it to start browsing your computer files,