Having Fun with Floating Letterform

Here are two really fun and playful examples of one of the features of After Effects, motion tracking. From what I gather, motion tracking allows you to manipulate a portion of moving video with the manipulation remaining in the same place regardless of the video's vantage point (e.g. if you apply the texture to a sign and pan around the landscape, the texture will appear to remain fixed to the sign). Although I do not fully understand how the effect is executed, it seems like a very powerful effect, one that could be used as a mask, such as in this video, or to follow an moving object, like in this video.