Similar profiles are creators related to the one you are looking at. You find them on the Similar Accounts tab of the profile page (login required; not available for Twitch). On Instagram the tab has three views: Similar Creators, one ranked list that blends shared followers, audience lookalikes, collaborations and creators from the same niche (the chips on each row show why an account matches); Notable Followers, well-known accounts that follow the creator, available once their audience report is unlocked; and Collaborates With, accounts that have published co-authored posts with the creator. On TikTok and YouTube you get one list of similar creators.
Use the suggestions to discover lookalikes for campaigns or benchmarking without running a new search: each suggested profile can be opened directly or added to a collection. For Instagram brand accounts there is also a shortcut into the Lookalike Lists feature, which builds a whole creator base from the brand's audience.