Why do I need a home server?

Simply put, there isn’t just a single answer for this. It depends on your specific requirements.
A list of possible answers could be:

• you have more than one computer in your home, and you need a centralized place to backup all the important files scattered around
• or you just want your family pictures in one place, but accessible from all the computers around the house
• you have a media player which can connect and play media files from the network, or a smart TV with similar capabilities (or even more important, not just one) – it is much simpler to have all your movies or music in one place
• you want to have access to your files while out of home (your “personal cloud” as hardware makers call it)
• you want to have a personal site (be it a photo gallery, a cooking recipes list or a technology demo) which you can’t or don't want to host somewhere on the net

Depending on what you need and expect, there are more roads you can take …