Sql Server failover clustering can be conceptually explained as a smoke-and-mirrors dns hack. Thinking of clustering in familiar terms makes you realize how simple a technology it really is.
Simplified description of Sql Server Failover Clustering
Imagine you have two computers: SrvA and SrvB
You plug an external HD (F:) into SrvA, Install Sql Server and configure it to store its database files on f:\ (The executable is under C:\Program Files).
Unplug the HD, plug it into SrvB, Install Sql Server and configure it to store its database files on F:\ in the exact same location.
Now, you create a dns alias "MyDbServer" that points to SrvA, plug the external HD back into SrvA, and start sql server.
All is good until one day when the power supply fails on SrvA and the machine goes down.
To recover from this disaster you do the following:
Plug the external drive into SrvB
Start sql server on SrvB
Tweak the dns entry for "MyDbServer" to point to SrvB.
You're now up and going on SrvB, and your client applications are blissfully unaware that SrvA failed because they only ever connected using the name "MyDbServer".