'Vending' is the -ing form of the verb 'vend', which means to sell something. On its own, 'vend' is a very formal, almost legal word. You will see it in contracts, in city rules, on official signs — 'No vending on this street' — and almost never in normal talk. If a friend sold their old bicycle, you would say they sold it; nobody says 'I vended my bicycle'. So do not think of 'vend' as a nicer word for 'sell'. Think of it as the word the government or a company uses.

There is a small but real difference in what kind of selling it points to. 'Vend' usually means selling goods in small amounts, in a public place, often without a proper shop — a person with a cart, a stall, a machine. That is why the two places you will actually meet this word are 'vending machine' (the machine that sells drinks and snacks when you put money in) and 'street vending' (selling things on the street). The person is a 'vendor', and that word is much more common than the verb — 'a street vendor', 'a food vendor', and in business English 'our vendors' just means the companies we buy from.

'Vending' also works as a noun for the whole activity or business: 'She works in vending', 'the vending industry', 'vending rights at the stadium'. For your daily English, honestly, you mostly need 'vending machine' and 'vendor'. Keep 'vend' as a word you recognise when you read it, not one you reach for when you speak.