There isn't really a set definition of 'Home Lab' and I'd personally describe it as a place that a user would use to learn, test or tinker. The user would normally be trying to accomplish one of the following:
Improve their skill set to apply at a job elsewhere.
Study for system administration, networking or Virtulization exams.
Use software such as; VMWare, VSphere, pfSense, FreeNAS and Windows 2012 server.
Things to consider before buying;
There are many things to consider before diving into the world of homelab's. The first thing you will want to consider is your budget, how much do you want to spend immediately to get your homelab ordered. There are hidden costs that you will also need to consider, do you go for a power hungry server running two eight core Xeon processors that'll boost your electricity bill or do you perhaps only need two low powered Hex core processors for what you're trying to accomplish? Where is the server going to be placed, how much noise is it going to make, what's the heat dissipation like?
Next thing to consider is, are you going to be running Virtual machines, if so what hypervisor are you going to use, ESXi, Xen, Hyper-V or KVM? Are you going to be building your own NAS, you've got many options such as FreeNAS, NAS4Free, unRAID, Windows server etc.
Still need more information, where can i find it?
The best thing to do, is just to google it! There are so many resources out there that you can use to decide on what it is that's best for you and fits your budget. Beyond that, send us a message well see what we can do, after all we're here to help!