Simple Definition:

Equity share is a type of ownership in a company [a business organization] where the shareholders [people who own shares] have a share of the company’s profits and losses. These shares represent the proportional ownership or equity in the company.

For example, if a person owns 10% of the equity shares of a company, they will receive 10% of the profits and also bear 10% of the losses of the company.

Very Simple Definition:

Equity share is when you own a part of a company and get some of the money it makes.