There is a difference between ‘A Lead’ and ‘A Sale’ in real life and online.
In CPA (cost per action), affiliate marketing and e-commerce, ‘lead’ and ‘sale’ are types of ‘actions’ (as in, cost per Action). CPA is quite simple: you get paid when your visitors click on the affiliate link and perform a needed action. Actions such as filling out the form, submitting email or a zip, signing up for a free trial, starting a subscription service will be counted as a Lead and actually buying something, where money exchange was made, is a Sale. Thus, actions that do not include a sale are called ‘leads’ and a sale is a ‘sale’ everywhere