Basic editing, sometimes called copy editing, is a level up from proofreading and, in addition to everything done in proofing, includes:
correcting incorrect or substandard usage (such as “can” for “may”);
checking and making style consistent throughout document;
checking overall clarity and understanding;
checking specific cross-references;
checking for proper sequencing (such as alphabetical or numerical order) in lists and other displayed material;
checking geographical references for accuracy;
checking numerals and math.