The jewellery is fired to a high temperature and is very strong. However, because they are ceramic, they can still be fragile if dropped onto a hard surface, so I would recommend putting on and taking off your jewellery over a soft surface.
If any marks get onto your jewellery, you can wash them off of the porcelain with soap and water and a cloth or brush.
Vases are glazed on the inside and on the back, with an unglazed and polished exterior. Handwashing with soap and water is kindest, to keep your ceramics in great condition forever.