There is a bunch of calendars that come with your calendar (if that sounds confusing, catch up on Calendar and Layers). What do they do? Who put them there?
Let us start by looking at what Google actually uses calendars for.
As a reminder: The word "Calendar" is used both for the Google service and for the calendars/agendas/diaries/layers contained in it. To differentiate: Google Calendar (uppercase) is the service. Which can contain several calendars (plural). Ready? Let's dive in!
Sounds more simple than it is. There are several categories of calendars:
Your primary calendar. For many people, this IS Google Calendar. When you say "see if I am free", you actually mean "See if there is nothing on my primary calendar".
Secondary calendars somebody may have created.
Public calendars (like your favourite team's games, or specific public holidays)
(Primary) calendars of co-workers
Resources (meeting rooms).
Google Calendar allows you to hide and show information by piggybacking onto the "calendar" metaphor, although those pieces of information aren't really calendars:
Contacts' birthdays. These get set either by your contacts (in about.google.com) or by you (in contacts.google.com).
Reminders (Keep notes that have a due date or set in Calendar)
Tasks (set in the Tasks sidebar or in Calendar).
For a while, week numbers and weather were available like that too. Week numbers are integrated properly today, weather has been dropped.
When you open the left-hand side bar in Google Calendar and click "+" next to "Other Calendars", you are greeted with the menu below. Here is what the options do.
This means "display somebody's primary calendar" - most commonly your boss'. Executive Assistants do this all the time.
You can create as many as you like (there are limits) by selecting "Create new calendar". Just be aware that you have just added a layer, and whatever you schedule on that layer is NOT on your primary calendar (so people will not see that you are busy). That may be exactly what you are looking for.
Resources mean "meeting rooms" in Google Calendar language. Every room has a calendar to show what time it is available. If your territory uses rooms (lucky you), you can subscribe to your favourite rooms' calendars.
These are read-only. They live in a curated directory and I have no idea who maintains them. They are accurate though. Being separate from your primary calendar, displaying these events will not impact your availability.
All calendars (primary, secondary, interest and even Contacts) have URLs. If somebody shared this URL with you, you can add it right away using this option.
This lets you import files from other systems, such as MS Whoosh. You will probably not need this.
You may have a calendar called "From Notes". It's whole purpose today is to tell you that you are old. When we went Google, some territories created a calendar like this for their folks and copied Notes calendar events into that calendar. It probably confused more than it helped, because it is a secondary calendar and thus does not block time in your primary calendar - see how it all falls together now? That calendar is empty today and will always remain so. If you have it - you can hide or delete it.
When you are fed up with a calendar, you have several options (look at the image on the right):
You can quickly hide and show the calendar. This is great if you have important, but highly polluting calendars such as a big team's vacation calendar.
You can unsubscribe from the calendar, which means that you need to add it back if you want to see it again.
You can hide it from the list, which means it is still in Google Calendar's settings, just not in your day-to-day list of calendars.
If you own the calendar, you can go into "settings" and delete the calendar. This will end the fun for everybody you may had shared it with, which is sometimes desired. You cannot delete your primary calendar.
This was your Calendar special - I hope this motivated you to make Calendar even more personal. Go and add the Yankees' schedule, create a Team Calendar and make it all around yours. That's what it is for. If you get overwhelmed, just remove as much as you need. No harm done. Thank you for reading!