Identifier

In Python name of any variable, function, class, module, and object is called an identifier. An identifier can start with a lowercase or uppercase character or an underscore (_) followed by any number of underscores, letters, and digits. All identifiers in python are case sensitive.

Example Variable: distance=10

In the above example distance is an identifier.

Example Function:  def calculateTotal(prices)

In this above example calculateTotal is identifier.

Example class:  class User

In this above example User is identifier.

Keyword or Reserve Word

Keywords are also called as reserved words in python. So keywords cannot be used as an identifier to name variables or object or functions. Few of the keywords are listed below.

Example: if, else, elif, for, while, break, continue, pass etc.

Following is the list of reserved keywords in Python 3. You can explore each keyword examples and detail on click of each.

and	except	lambda	with
as	finally	nonlocal	while
assert	false	None	Yield
break	for	not
class	from	or
continue	global	pass
def	if	raise
del	import	return
elif	in	True
else	is	try

Python 3 has 33 keywords while Python 2 has 30. The print has been removed from Python 2 as keyword and included as built-in function