What does "@" next to a String means in C#?

Question

after i saw this program, i was wondering can it be used as a preformatt marker or something
https://code.sololearn.com/cEh3uNQ0Hg8Y/?ref=app

Answer 1

https://stackoverflow.com/a/556142/9132046

Answer 2

Mert Yazıcı thanks bro/sis 😊