为给定的代码添加必要的注释以提高可读性。

代码片段：
```
def calculate_sum(a,b):
    result = a + b
    return result
```
```
# This function calculates the sum of two numbers.
# It takes two arguments a and b and returns their sum.
def calculate_sum(a,b):
    result = a + b  # Add the two numbers and store the result in a variable called result.
    return result  # Return the result of the addition operation.
```