Common ordinary equity is like owning a toy box with some toys inside. The toy box represents the company and the toys inside represent the ownership or shares of the company.
When you buy a share of common ordinary equity, you are buying a small part of the company. This means you become a part owner of the company, just like how you become an owner of your toy box when you buy it.
As a part owner, you get to share in the company's profits (money the company makes) and losses (money the company loses). If the company makes a profit, it might pay out some of that profit to you in the form of dividends (like when your parents give you some money to buy a new toy for your toy box). If the company loses money, you might lose some of the value of your shares.
Overall, owning a share of common ordinary equity means you have a little piece of the company and can participate in its successes and failures.