Many websites and programs change your browser settings or homepage. Often for the purpose of showing you more ads.

Likewise, many browser extensions and toolbars insert additional advertising into webpages as you browse. Annoying as this can be on its own, downloading all these extra ads also slows down your web surfing.

The options to restore your homepage and default search engine will only be available if they have been altered by something. If the options are disabled, it means there is nothing to fix.