OK, there are libraries all over the world. Each library contains thousands (or tens of thousands) of books, and each book has so many pages. For example, let's say you wanted to read my book, Growing Doobie For Fun And Profit, and the only copy of that book is at the Walt Disney Memorial Library in Marceline, Missouri. The WDML can be said to be "hosting" my book. Within that book are several hundred pages; the paragraph you need is on page 420. The book can be said to be "hosting" that page.
In internet parlance, a "server" (in essence, a computer that does nothing but store data) is essentially like a library. A server may host one "book" (website), or several thousand. Similarly, if a single book were so big that no one library could contain all of its pages, some websites (Google, YouTube) are so big that no one server can handle them all. Further, it's good business to have several backup servers, in much the same way that it would be wise for me to have my book in several libraries, in case the WDML were burned to the ground, raided by brigands etc.
When you access the internet, your computer is making a connection to a server - your Internet Service Provider. That server then connects to all of the other servers its users are accessing; the Google, YouTube, the DIS boards, my website, etc.