What does "for(;;)" do in C#?

Is it kind of like "while(true)"?

Yes. It loops forever.

Also note the comment by Andrew Coleson:

Languages like C don't have built-in boolean primitives, so some people prefer for(;;) over while(1)

Correct. Note that the braces of a for loop contain three parts:

1. Initialization code
2. A condition for continuing the loop
3. Something that gets executed for each loop iteration

With for(;;), all of these are empty, so there is nothing done to initialize the loop, there is no condition to keep it running (i.e. it will run indefinitely) and nothing that gets executed for each iteration except the loop's content.

Yes, it's an infinite loop. Same idea/effect as doing while(true) { ... }

It doesn't have an end condition, so it will loop forever until it find a break, as you already guessed.

I might also add that it looks like 2 smiley faces winking at you

for (; ;)

maybe that's why some people like to use it.