The difference between a joiner and a carpenter can be summarised as follows:
A joiner constructs items by joining pieces of wood without using metal fasteners, screws or nails. A carpenter will then take these items and fit them on site usually using metal fasteners, screws and nails and a carpenter would also undertake tasks such as fitting locks and door furniture.
This is a very important distinction. Joiners and carpenters do different things.
So if you want a door or a window made or repaired you will require the services of a joiner. If you require the installations of wooden fixtures on site you will need the services of a carpenter.
Another very important distinction is that joiners construct items at a bench, in a workshop. Once these items, such as interior and exterior doors, windows, stairs, tables, bookshelves, cabinets and furniture are completed, they are passed to carpenters who use their carpentry skills to install them on site.
Furthermore, the equipment used by joiners and carpenters are very different. Joiners are based in workshops and the equipment they use often tends to be large and heavy, such as mains electricity powered saws used create and cut joints. Carpenters, by comparison, use equipment that are relatively light, portable and can be moved around while on site.