LinkedIn delivers relevant ads (and measures their performance) to members when they are on third party applications and sites through its LinkedIn Audience Network and third party integrations, such as "Sign In with LinkedIn."
LinkedIn uses data that you provide to create your account, as well as data that it receives from its partners, for this purpose. Other than hashed or encrypted identifiers, LinkedIn does not share any of your personal data with third parties for this purpose. LinkedIn does not use these partnerships to learn your personal interests or otherwise build a profile of you.
You can always opt out if you do not wish to be shown personalized ads outside of LinkedIn.