Account verification started in May 2013 when the blue badge was introduced. It was made to verify public figures and personalities with large audiences. After a while, many politicians and celebrities used this feature.The latest one, the gray badge, which was launched in October 2015, is for local businesses with valid addresses. It was a no-brainer for companies, big or small, to adopt this one.
Because people notice badges first even before seeing the contents of a page, having it gives an advantage of a great first impression If you see a blue tick on the page or profile that means Facebook has confirmed that this public figure or media company or brand is genuine.If you see a grey badge on the page that means Facebook has confirmed that the page belongs to a genuine organization or business house.
As you can see in this example, blue badges are usually granted to the official brand or personality. The grey badge is given to local businesses at specific locations.
Both signify the authenticity of the page.