This is the general term used for all salted vegetables, and many vegetables, including cucumber, aubergine (eggplant), daikon, hakusai and mustard leaves, are used. Japanese cucumber and aubergine are a lot smaller and more delicate in flavour than Western varieties, so look particularly for those.
Shio-zuke (salt-pickled vegetables) can refer to a number of vegetables including, from left, aubergine, radish and cucumber.