Where you have been
The explorer keeps a note of every place you open, on your own device. We cannot see it, it is not attached to any account, and clearing your browsing data removes it.
Reading your browser…
Where this is stored
In your browser's local storage, which is a small store that belongs to this site on this device. Nothing is transmitted. There is no account to attach it to, and no server holding a copy, which also means the list does not follow you to another device or another browser.
If you want a copy that does travel, use Export CSV. That gives you a plain file with the name, address, coordinates and timestamp of everywhere you have been, which you can open in any spreadsheet.
Keeping the good ones
History is automatic and capped, so older entries fall off the end. Anything worth keeping should go to saved places instead, where it stays until you remove it and where you can give it your own name.