What is the purpose of the "at" sign in WordPress?

What is the purpose of the "at" sign in WordPress?

I've been developing on WordPress for a couple of years now and I keep
seeing the "at" (@) sign in themes and plugins code.
What is it for? Does it serve a special purpose in WordPress? Or is it
just a general programming documentation thing? I haven't been able to
find anything about it thus far.
Examples of what I've seen in code:
@see woocommerce_output_product_data_tabs()
@uses load_theme_textdomain() For translation/localization support.
@since Twenty Thirteen 1.0
@return void
@param string $title Default title text for current view.
If there is documentation somewhere on what this is and how it should be
used, I'd love to find it since this question has been bugging me for a
while.