Google has record of everything you do on internet. It collects information regarding searches, sites and youtube videos you visit. You can see everything inside My Activity page. Everything you browse on internet can be seen and deleted too.
The list includes every activity you do while sign in is tracked under my activity. If you are using Google chrome it will include every searches, websites etc with date and time. And, best part is all the information is searchable. So, if you know about a part of website, you can just search and flashback everything.
Some people may think, this is a privacy breach. So, if that worries you then you can go to Activity Control page to turn this off. Below is the screen shot of activity control page.