conviction means finding that person guilty of the crime right? according to my question he wasn't and the case was dropped so what i am asking now is will it still count against him if he was arrested for the charge in the first place.
Actually, Immigration has its own definition of "conviction" and that does not necessitate a finding of guilt (this is why it is never easy to answer such questions and there is always the chance that certain details could result in it being a conviction for immigration purposes), but based on what you've indicated it does not appear to be a conviction (only way to know for sure is to get the records and research based on that if you know how to conduct such research, but better off hiring an immigration/criminal defense attorney). That by itself is not likely to "count against him" as you say, but you are really talking about admissibility which involves much more than just criminal issues. Considering the fact that your brother already has this criminal issue, it is likely to draw attention to his application warranting a closer look and it is in his best interests to not pursue any benefits from USCIS without an attorney.
a 5 thousand bail, not going close to her and any of her family members and also siezed gun handling privileges dose were the things he was told to do until an outcome on the case was established(no bill), so am kinda confuse as to how immigration see conviction differently?? thanks for ur detailed response by the way
Immigration just has its own rules regarding whether something is a conviction and it involves reviewing the original charge, the outcome, and conducting research. The crossover between immigration and criminal law is very complex and even experienced attorneys sometimes struggle with it and can get it wrong. No matter how much detail you provide, there would be no way for an attorney to comfortably give you the answer you seek without reviewing the actual documents and conducting research; if it was possibly to safely do so on a forum such as this, you would already have an answer. Anytime someone has a criminal issue (even what most would consider minor), they generally need to consult with an attorney directly because of the potential complexity and the risk of giving bad advice on incomplete information. I'm sorry I cannot give you much more help/direction except to tell you to get your brother to an immigration attorney as soon as you can.
Let me say this though, your brother should not get it expunged unless/until he has numerous certified copies of the documents related to the case. Sealed/expunged records do not matter to Immigration - you must provide certified copies of documents from the cases, so be sure to have many of those ready (certified copies of arrest and booking reports and certified copies of the case dispositions at a bare minimum) before the record is sealed/expunged.
If money is an issue, your brother may be able to get assistance form a local area legal aid organization or other non-profit offering free/low fee legal immigration services to low income persons.