Now the other writeups are quite accurate, except
for the beach-and-palm trees thing.
You need neither, in fact, it is entirely
possible not only to attach the net to
wall-mounted hooks, but also to sleep in a
sufficiently long and straight specimen. I should know
because I did for a few years (and in fact still would
if most of the strings on the side near the window
had not given way ...).
Attaching the wall plate was relatively straightforward
except my father had to drill the holes
as I didn't have a percussion drill at the time.
The major pain in the ass when sleeping in a hammock
is chillyness, even in midsummer I used to toss the blanket
and look for the sleeping bag a few hours into the
night.
I have been told it's bad for your back to sleep in a
hammock, but this is most likely as much of an urban legend
as not being able to barefoot in snow.