In the play A Midsummer Night's Dream, what is the play within the play about?William Shakespeare

In Shakespeare's A Midsummer Night's
Dream, Bottom and the other mechanicals (tradesmen) go to the forest to avoid
scrutiny to practice the play that they will present as part of the celebration for the
wedding of Thesus, Duke of Athens, to Hippolyta, Queen of the
Amazons.

Their play is to be called The Most
lamentable comedy and the most cruel death of Pyramus and Thisbe.  Before
they go into the woods, the tradesmen, who fancy themselves great wits and actors,
discuss the play.  Bottom, the weaver, says that he will play the lover Pyramus, who
dies; he believes that he will be so good that the audience will cry.Flute, the bellows
mender, who has been assigned the role of Thisbe, wonders how he will play a woman when
he is growing a beard. Quince, the carpenter and director, tells him he will have a
mask. Snug, the joiner, plays the lion and worries that he will not know his lines in
time when all he must do is roar.

Foolishly, Bottom wants
to play the lion, too, but he is to be killed by this lion. Robin Starveling, the
tailor, will play Thisbe's mother, and Tom Snout, the tinker, will be Pyramus's father. 
When Bottom describes how he will roar if he plays the lion, Quince tells him he will do
it so loudly that he will frighten the duchess and the ladies, getting them all hanged. 
Bottom says he will not be loud, but Quince will hear no more.  He tells the troupe to
memorize their lines by the next evening when he will meet them all in "the palace wood"
because if they meet in town they will be "dogged with company" and everything known
about their play.  They agree to meet at the duke's oak
tree.

The next day when the tradesmen meet to rehearse,
Puck and Oberon and his wife are also present in this woods.  The king and queen of the
fairies, Oberon and his wife Titania argue with one another, showing that the natural
world is at odds with itself. As Titania lies in the woods, sleeping, the tradesmen
arrive and comically dispute their roles among themselves with Bottom telling Quince he
will need two Prologues so that the ladies will not be frightened by the sword scene or
the lion. The logistics of having a wall through which Pyramus and Thisbe can talk and
of the moonlight are discussed. At this point, Puck enters to distract the men and to
protect his queen.