There are several motivating factors that would cause someone to block anyone else on Facebook. For example, if you’ve got a stalker, or a spammer that just won’t quit. Or perhaps a parent who can’t keep their nose out of your business, or an ex who can’t keep their eyes off you.
There are two ways to go about. The first is the simplest way. Visit a person’s profile page and scroll all the way down to the end of the left sidebar. ‘Report/Block This Person’ is apparent on a link there. Click on this link and confirm that you want to block this person.
The second way is this: under the ‘Account’ menu item, you should select ‘Privacy Preferences’. Down at the bottom of the page there is a ‘Block List’ option, and you should click on the ‘Edit your lists’ link.
You will be directed to a page, where you can change your block lists settings. This includes adding the name or email of the person you would like to block, application invites, and event invites. You will also be able to modify your block lists, and you can remove any item on your block list at any time. Any person you block will not receive any kind of notification that they have been blocked by you.