Quality Control: the translation is checked internally before being delivered to you. This consists of: verifying that the instructions were followed to the letter, checking for inconsistencies, verifying numbers, layout and formatting, checking spelling and grammar, verifying line breaks and capitalization.
Proofreading: a second linguist proofreads the target text only. The goal of this proofreading step is to correct spelling, grammar, typography (capitalization, punctuation, typographical errors), style and syntax (structure of phrases).
Bilingual revision: a second expert linguist compares the target text to the source and makes any necessary edits, ensuring the translation is correct (identifying mistranslations, omissions, etc.) and that any predefined terminology has been used appropriately.