Translation of certain documents may be necessary during the immigration process.
When submitting supporting documents to USCIS, it's required that all documents not originally in English be accompanied by certified English translations. This is common as many different countries issue documents like birth certificates and other official documents in many different languages, from Chinese to Russian and everywhere in between. The USCIS doesn't translate these for us, so when submitting such documents, we must provide an accompanying translation. It does not need to be a professional company doing the translation. Any capable person can do the translation (but it's best if it's someone other than the applicant). When we say it must be "certified", that simply means whoever translates the document must write on the page a certified statement similar to:
"I certify that I am competent to translate (language name) to English, and that this is a complete and correct translation"
Below this statement, the translator should date and sign this statement. Although not required, it may help bolster the seriousness of your case to have the certified statement signature notarized.
You must include both the non-English copy and the translated document.