A method to pass the lock screen and get into the operating system to use it. Users are required to slide their finger on a predefined position on the lock screen. Popularised by Apple's iPhone, and Apple has patented the whole vague idea, thus making it one of the most ridiculous patents yet.
There hardly could be a method to unlock the screen by doing a certain action on the screeen itself without violating that patent. For example, Apple also claimed that a tap on the screen is a 'zero-length sliding'. Microsoft introduced a picture password unlock screen to Windows 8, but that is also essentially a slide to unlock.
Google has improved and diversified the slide to unlock on Android in many ways, so that now they look so very different. Yet, Apple wants to ban Android products for this patent or wants the manufacturers to pay a ridiculously high patent fee for this.
A Japanese man: You know, we used to slide the door to open it and get into the room.
An Apple guy: Hey, that sounds like slide to unlock to me. You violated our patent! You'd better stop using that door.
A Japanese man: We had those since thousands years ago?
An Apple guy: Doesn't matter. We've got the patent. See you in the court.