OAuth
An authorization standard that lets an application access another service on your behalf, without ever seeing your password.
When you connect an app to HubSpot with OAuth, HubSpot asks you to approve the access the app requests, then gives the app a token. The app uses that token to call HubSpot's API, within the permissions you approved.
You can revoke the access at any time, and the app never holds your HubSpot password. Tokens should be stored encrypted and never sent to the browser.