First of all it is は not わ。は is pronounced "wa" when it is used as a particle. が is a particle marking the subject, a similar concept as in English. は is a "topic marker" which has no analog in English. It is practically used everywhere in Japanese, and is one of the unique features of Japanese (and Korean). It's probably not an exaggeration to say that it goes to the soul of the language. It is difficult to pick up quickly because it has many uses difficult to grasp at first, including doubling up as a subject marker like が, as well as carrying subtly different connotations similar to the difference between English "the" and "a". Take some examples. が and は may be used in the role of subject marker as in: ほんが つくえの うえに ある。(The/A) book is on the desk. が as subject marker. ほんは つくえの うえに ある。(The/A) book is on the desk. は as subject marker. But は can be used as an object maker as well. すいえいは やめて テニスを しましよう。 は in this case is an object marker, and may be translated literally as: "As for swimming let's drop it, and let's go play tennis instead" (subject is "we") So you see the topic marker in action. It topicalizes something like English "as for...". It can attach to a subject, an object, or even to another particle (では, には). Whichever is the case, it always topicalizes it, i.e, draw the attention to what it marks. From this topic marking function comes a few different usages. It will take a lot of time and work to get to pick up all those different usage patterns. You'll have to study a lot of different case examples to get the hang of it. If you want to see more detailed explanation, you may check this link. http://www.japaneseprofessor.com/lessons/beginning/the-topic-marker-wa/

you said "わ"is "は”what is to be a theme topic ."が"only to stand of sentence's theme?do you understand? you can take me in your friend ,i will for example to you to make you clear.

I see your question's been answered already, but I thought I'd share this video as it was what really got me to understand early on in my learning. https://www.youtube.com/watch?v=UCiIAXVr1FU He's got many other good, short and informative videos too. Hope it is of use!

Oh- Oops! >w<;; I am aware that は replaces わ when used as a particle, I just forget to type it as that. Sorry, sorry.. Anyways thank you for the help~ I will try my best to get a grip of it.