When you sign up for a Calendar account, you'll get a screen that looks like this:
You will be asked to enter your first and last name. Then, the third space listed above is what is known as your Calendar link. This is your personal link that you can share with others when you want to share your calendar with them and it personalizes it for your use.
If you have a LinkedIn, Facebook, Twitter, Instagram account, or other social platform, you may already have seen these types of personalized links that work in much the same way.
When you first sign-up, the Calendar app will most likely suggest one for you or you can add your own. After submitting, Calendar will let you know if it's available. If it's not available, it's because it's already in use by another Calendar member. Then, you'll have to adapt it by using a last name, including a middle initial, or adapting it in a way that makes it unique but still personal to you.
You'll be able to find this Calendar link under the menu at the top right-hand corner of your screen:
The boxes on the right side of the link can be clicked on. This will copy the link to your clipboard so you can share it with others.