Most reef tanks start as frag tanks per say...
A real frag tank will be a tank setup for the sole purpose of growing coral frags. It will have racks with frags on them and be nothing but frags. Most times you will find these type of tanks at the
LFS with the coral for sale.
A reef tank will most of the time, be somewhat established and while it may have coral frags growing, it will be like a forest of coral and rockscapes.
These are pictures of frag tanks or prop tanks (Propagation). Pics off nano-reef or reef central.
A coral only tank is quite easy to maintain IMO. Though like ATP said, you'd be doing something everyday. Provided you have the right light, and enough flow. Maintain it just like a normal nano reef. Start with the tank, light,
live rock, sand, and saltwater. Then as the tank becomes established add some coral frags. Light is your most important factor in coral tanks.