"Respondent has committed fraud on the community estate." what does this mean???

It's a $6 phrase saying he violated his fiduciary duty and such, should reimburse the community for the bad thing he did. It's divorce litigation posturing and probably unlikely to be the most incendiary phrase he is going to pick out of the petition. Read a little more from a practitioner writing for a lay audience - http://www.heilalalaw.com/1/post/2012/09/joint-managing-community-property-vs-sole-managing-community-property.html

If it's in the petition that you filed, you should know what it means. It is typically included in a petition when the other party wants a disproportionate share of the estate. In layman's terms, his actions harmed the community estate in some way. You can google "fraud" for the legal definition.

It means that there is an allegation that he spend money or transferred property outside of the marriage without the other spouses consent. For example, he spent $5,000 in Las Vegas on some women. You did not agree to the transaction, and want the money back in the estate. It has been spent, maybe he has $100,000 in retirement, and you want more out his retirement because of the money he spent in Vegas on someone who was not the natural object of your affection or it was not agreed.