Ok, so If I put both my hosts into a HA cluster and I have my VM's installed on a separate storage server and one of my hosts goes down VSPhere will be able to reboot my VM's on the other host?
Yes, assuming both hosts have access to the storage and HA is configured properly.
And VMotion is just for planned maintenance?
Not only for maintenance, but also for e.g. load management/distribution.
André