“First-party data” in marketing and advertising refers to data owned by you or your business, such as data you collect customers or other consumers visiting your website. It is considered the highest quality customer data.
You, or your business, is in turn responsible for ensuring its protection and ensuring the customers (or regulators) privacy rights.
“Second-party data” is first-party data owned by someone else that you have bought, licensed directly, or have a partnership with. Data protection and privacy rights are shared.
“Third-party data” other data collected or aggregated, typically by data brokers, from a wide variety of sources. It is the least reliable data as collectors and their methods are not transparent.