Okay, imagine you have a bowl of candy that you want to share with your friends. You have 10 pieces of candy in the bowl, but you only want to share 5. So, you tell your friends that you have 5 pieces of candy to share, and your friends agree.
In a company, shares authorized is kind of like the number of pieces of candy in your bowl. Just like you only wanted to share 5 pieces of candy, a company decides how many shares of its stock it wants to share with the public. This is called the "authorized shares."
Let's say a company determines that it wants to share 1,000,000 pieces of candy, or shares, with the public. This means that they have authorized 1,000,000 shares of stock. But just because they authorized 1,000,000 shares doesn't mean they have to share all of them at once.
They can choose to only share a portion of those authorized shares initially, and keep the other shares in their metaphorical candy bowl for later use. For example, they may sell 500,000 shares to the public and keep the other 500,000 shares for future use or for certain investors.
So, in summary, shares authorized is how many pieces of candy the company has in its bowl that it can choose to share with the public. They can choose to share some or all of those authorized shares at any given time.