Imagine this: your library is trying to step up its game and compete in the Internet age. Rather than you browsing the shelfs, trying to remember how the Dewey Decimal works, you'll enter your book selections from your phone. A librarian will then bring your books to the front desk.
You place your book order on a busy weekend morning. Rather than getting all of your books, the librarian just brings one back. Sometimes the librarian even asks for your book back, tells you to walk out the door to make room for others, and lets someone else read their book for a bit. They then call you back in, shuffling you and the other book readers in-and-out.
What's going on? Is the librarian insane?
This is the life of the Linux's memory management unit (librarian) and processes (you and the other book readers). A page fault happens when the librarian needs to fetch a book.
How can you tell if page faults are slowing you down, and - above all - how can you avoid being shuffled in-and-out of the library?