Difference beteween stuff and replace function in sql server

STUFF function is used to overwrite existing characters. Here is the syntax of stuff function

stuff (Expression, start, length, replace),

Expression is the string that will have characters substituted

start is the starting position

length is the number of characters in the string that are substituted

replace are the new characters interjected into the string

Here is the   example of stuff function

SELECT STUFF('anil kumar', 1, 2, 'sun');

Output this query = sunil kumar

REPLACE function to replace existing characters of all occurrences.

Using the syntax REPLACE (string_expression, search_string, replacement_string), where every incidence of search_string found in the string_expression will be replaced with replacement_string.

Here  is the example

select REPLACE('Sunil Kumar asp.net devloper','Sunil','Anil' )

output of this query is: Anil Kumar asp.net devloper