Washing veg and fruit

'Wash before use' is a well-known instruction. I don't know what it means. Does it mean washing-up liquid and warm water and scrubbing? If I do what I usually do, which is hold them briefly under the cold tap, the water beads on waxy surfaces, and what good is that? I do put spinach and greens into salty water - I'm thinking more of apples, pears and grapes. How do 'they' expect us to wash such fruit before use?