Learn in the textbookThe Foundations of Electronic Payment and Data Exchange
DefinitionCashless payment (キャッシュレス決済) is an umbrella term for all the ways of paying without notes or coins.
ExplanationCards, QR codes on a smartphone, IC cards: whatever the method, anything that avoids cash belongs here. Sorted by when the money leaves you, there are 3 kinds: prepaid, where you load money first; pay now, where the price is taken from your account as you pay; and pay later, where you are billed together afterwards.
Memory hookCash plus "-less" (without). It names a condition, "no cash", rather than any one method, which is why it is an umbrella term.