It is a common programming practice to indent code. **Indentation** uses spaces or tabs to separate the code for better visualization. This is important for code readability. 

>In Python, indentation is part of the syntax.  

```
def foo()
    print("foo") // 1st level indentation
    if True:
        print("True") // 2nd level indentation.

print("Source") // No Indentation, part of source.

```

The code snippet above describes how to indent code in Python. Failing to adhere to these principles can lead to the "IndentationError: expected an indented block" error.

> When we say indentation, it is basically any consistent white space. However, it is common to use 4 spaces for indentation or apply tabulation to the code.  

To resolve this error, check the following things:

1. Check to see if you have left alone an `else:` part of an `if-condition`, and check if the indentation is missing after conditions, loops, etc.







x = 5
if x == 2:
  print("x is 2") #indented
else:
print("x is not 2") #unindented

x = 5
if x == 2:
  print("x is 2") #indented
else:
  print("x is not 2") #indented

2. Check the indentation of statements inside the function.  



def print_msg(the_msg):
"""this doctring not indented"""


What is "IndentationError: expected an indented block" in Python?

In Python, "IndentationError: expected an indented block" occurs due to improper code indentation, needed to maintain code structure.