what does x reprsent in this code ?

[pyzyx3qwerty]

food is one of the things defined under the function. You will frequently see that as you go through functions.
So, for example:

def abc(name):
   print(name)

In the above lines, name is one of the parameters. Now,

n = "pyzyx3qwerty"
abc(n)

in the above lines, it will n out because n represents name in the lines