Use of 之 in Mandarin Chinese

[biritululo]

 你们好(ni3menhao3)，

Can anyone explain to me the use of 之 (zhi1) in Mandarin? Is it like 的 (de)？What does it indicate? I know it's a particle but I'm not sure when or how it's used.

谢谢 (xie4xie4)！