The simplest way to explain about Lucid dream is.
Lucid dream is a dream in which one is aware that he/she is dreaming.The term was coined by the Dutch psychiatrist and writer Frederik (Willem) van Eeden (1860-1932).
In a Lucid dream , the dreamer can actively participate and can do anything he/she wants to do.The dream environment changes according to your wish, Whatever you wish it happens in your Lucid dream.
Anyone can have Lucid dream , But it needs regular practice to sustain the ability of lucidness in your dream.