Org-mode uses begin...end
blocks for various purposes from including source code examples
(see Literal
examples) to capturing time logging information (see Clocking work
time). These blocks can be folded and unfolded by pressing
TAB in the begin line. You can also get all blocks folded at
startup by configuring the variable
org-hide-block-startup or on a per-file basis by
using
#+STARTUP: hideblocks
#+STARTUP: nohideblocks