Summary is how you do a collapsed section. The bit after details= is what the section is named. The bit in the middie is the part which gets hidden.
It gets mixed up if there is html or other formatting inside, so it is best to lay it out like this with a clear empty line between all the parts:
This bit is not hidden
[details=HIDDENSECTION]
This text will be hidden
[/details]
This bit is back in the open again
ends up like this:
This bit is not hidden
HIDDENSECTION
This text will be hidden
This bit is back in the open again