Can someone help explain Catch-22.I am having trouble understanding the writing. I do think parts are funny but I don't understtand what is true...

Joseph Heller's Catch-22 is my very
favorite of all novels. I was lucky enough to be taught it in senior English in high
school, and I hope you are doing the same. It is totally fiction, of course, but most of
the crazy antics described in the novel are supposed to happen to the characters. It is
an anti-war satire of great magnitude, and Heller's absurdist humor is aimed at various
established systems and concepts of which he has little respect--particularly the
military, commercial profiteering, and the very slight difference between sanity and
insanity. Yossarian, who everyone believes is crazy, is about the only sane character in
the novel. The rest of his comrades border on the insane, but since they are all alike,
only the very different Yossarian stands apart. Heller's primary point in the novel is
the futility of war. He satirizes it through Milo Minderbinder's selling out his own men
for financial profit; through  inept leadership; and through the concepts of bravery and
cowardice. Yossarian has become one of American literature's greatest anti-heroes, and
the term Catch-22 has become a catch-phrase for any excuse, absurd rule or guideline
that arises.