Functionality: editing of text (even fictional tags), links, images (cut, resize, compress), forms, title, meta tags, hidden elements, multilingual sites, creating new pages from existed ones.
It has image compressor which can reduce size of an image by 80%, filemanager. Code quality remains the same, as if it was edited by a human. Purity can edit all pages at once, so you don't need to edit every page separately. System doesn't influence a website functionality. There are 2 languages available: Russian and English.