https://techcrunch.com/2022/12/13/a-quick-guide-to-all-the-checkmarks-and-badges-on-twitter/

Elon Musk-led Twitter is shaking up its verification system. Instead of one checkmark, now there are multicolored checkmarks to denote different things. This could be very confusing for users to track. So here’s a handy guide to all checkmarks and badges on the social network.

Blue checkmark: It currently means two things. 1) Account with this checkmark is a legacy verified account (read: verified in the pre-Musk era). This was used to mark a notable account representing a politician, a celebrity, or an activist. This was to prove that the said person is indeed who they are claiming to be. Musk has said that the legacy checkmark will go away in a few months. 2) Account with the blue check mark can also mean that the person has subscribed to it. The only way to know the difference between the two of them is to click on the blue checkmark.