Complex sentence: A folding editor is a text editor that supports text folding or code folding, a mechanism allowing the user to hide and reveal blocks of text--typically this is done to allow the user to better see the overall structure of a document or program.
Split into simpler sentences: A folding editor is a text editor that supports text folding or code folding. These allow the user to hide and reveal blocks of text--typically this is done to allow the user to better see the overall structure of a document or program.