To determine what these mean, look at the built-in help from fdisk. Details may differ based on your implementation; for mine, that looks like this:

Command (m for help): m

Help:

  DOS (MBR)
   a   toggle a bootable flag
   b   edit nested BSD disklabel
   c   toggle the dos compatibility flag

  Generic
   d   delete a partition
   l   list known partition types
   n   add a new partition
   p   print the partition table
   t   change a partition type
   v   verify the partition table

  Misc
   m   print this menu
   u   change display/entry units
   x   extra functionality (experts only)

  Save & Exit
   w   write table to disk and exit
   q   quit without saving changes

  Create a new label
   g   create a new empty GPT partition table
   G   create a new empty SGI (IRIX) partition table
   o   create a new empty DOS partition table
   s   create a new empty Sun partition table

...so:

• d deletes a partition (presumably your script was developed for a version of fdisk where if there's only one partition, there's no prompt over which to delete).
• n creates a new partition.
  • p indicates that it's a primary partition being created.
  • 1 indicates that it should be primary partition #1
  • 1 indicates that it should start at sector #1
  • the following blank line accepts the default end sector
• w writes changes to disk.

Try this and adjust for your conditions:

#!/bin/bash

HEREDOC_VAR_1='p q ' 
echo $HEREDOC_VAR_1

HEREDOC_VAR_2='n q ' 
echo $HEREDOC_VAR_2

echo "$HEREDOC_VAR_1" | fdisk /dev/xvda
echo "$HEREDOC_VAR_2" | fdisk /dev/xvda