Who needs to file ADV?

Good day, could you please clarify for me who exactly is required to file an ADV, or an Adviser's Registration Depository Form? Is it mandatory for all financial advisors, regardless of their client base or assets under management? Or are there specific criteria that determine eligibility for filing this form? Additionally, are there any exceptions or exemptions to this rule that I should be aware of? Thank you for your assistance in clarifying this matter.