What is charter in 10 20 words

A charter is a legal document that formally establishes a corporate entity. Charters are issued by national or provincial governments. Before being chartered, the company may have existed as a partnership, sole proprietorship or similar structure. Most charters include the corporation's name, the location of its head office, the date of incorporation, the amount or type of stock to be issued, and any restrictions on areas of business activity or further share issuance.

From Google:

charter (noun):

document confirming creation of borough, company, etc.