Text and cover weights are figured differently, so a 50 lb cover is not lighter than a 70 lb text. Coated paper has a smooth clay surface coating which takes four color printing very well but is not much good for art. It is weaker, and is affected by moisture. Coated is used for printing magazines and shiny brochures. It is harder to recycle.
Bond is usually lightweight and smooth, and is used for copy machine, laser printing and typing.
Some bond used for stationery is quite elegant with a high rag content and watermarks. Color printer paper is also of better quality, with a surface that is less likely to bleed through with ink jet printing. Cover is heavy weight used for booklet covers, folders and cards. It can have any surface texture and often is made to match a line of quality text and envelopes. Duplex cover is two sheets of quality text laminated together, usually two colors.