How to explore my computer harddisk from any device via internet?

Well, there are a few ways to access your PC files remotely using Internet. A few of them have been explained here.

1. TeamViewer
It Is one of the trustworthy means of accessing your PC remotely. It Is available on Linux, Mac and Windows. They also have apps for Android and iOS. But the mobile apps work for transferring files from your remote PC.
There are a couple of Remote Desktop utilities available, yet TeamViewer has been treated as the most trustworthy of them all.

2. FTP servers
You can set up FTP server for your PC and grant Internet access to it. However, this method exposes your PC to security threats. Your PC needs to be in a switched on condition always for this to work.

3. Use network attached storage
You can use the NAS or Network Attached Storage devices. Most of them have support for accessing the files over the Internet. But, they are most insecure way of making your files available on the Internet. You may also connect a USB drive to the port on your router if it supports one. This drive will be accessible on your LAN.

4. Use VPNs
This is one of safest and secure ways to connect your PC to Internet and access it remotely. You will need to set up a VPN server on your home network and now, your PC will be a part of your LAN. You can access the local storage of your PC remotely.

There are multiple ways to approach this problem. So depending on how you plan on solving this, the solution may differ.

1. Make your computer a server - Making your computer a server and then letting the user access the content using username and password is a good option. This way you can access the content from any device. Few issues with this method is that you have to make sure you have proper security in place before making your computer a server. It also requires your computer to be on all the time, while you are away from computer.

2. File Transfer app - You can use file transfer apps like Dropbox, Google drive and mediafire to create virtual drive. This way you can access those files from cloud as well from Wifi over local area network.

3. Remote Desktop - You have plenty of apps like Windows Remote Desktop, Teamviewer and VNC. You can choose from one of these apps to transfer the content from any device.

Depending on how you wish to get the data, you can choose one of the three options explained here. I suggest using apps like teamviewer or even cloud apps like dropbox.

What you can do is running an FTP server on the host machine and then get an FTP connection client on the machines you want to use to connect to the home computer. You can then get the IP address of the home computer port, forward it and then you can use that IP address to connect to the computer from anywhere.