Editing involves checking and correcting text that was previously translated by a different translator from the source language into the target language. This is an important step in the translation process and is used to improve the flow of language translated by a non-native speaker, to check the accuracy of the translation as compared to the original, and to ensure that there are no spelling or grammar errors remaining in the text.
Proofreading is a similar service to editing but is generally done as a third step, to read over the translation and make sure that the overall flow and style of the document is accurate and appropriate. The goal of editing and proofreading is to ensure that the text is not only free of mistakes but also reads as if it was originally written in the target language.