The most basic way to understand what a "timelapse" video is, watching something that was captured in "real-time" played back at a much faster speed.
Essentially it's a video technique in which a subject matter is captured over a given length of time where the resulting video clip is assembled or created in such a way that your viewing that subject over a much shorter duration. Almost like being viewed in "fast forward".
Here's a simple example video of a timelapse that was captured over a 15 minute period, where the final timelapse video is 8 seconds in length.
Therefore, in this particular example above, you're able to see and watch all the happens over a 15 minute period in just 8 seconds!
This is the magic of time lapse, being able to watch the effects of time passing in short durations. Understanding this concept can allow us to apply this technique to situations and subject matters that would benefit from time-lapse capture. Specifically in subject matters where changes over time or progress being made is the main focus.
Thus the power of time lapse can really excel where the subject matter is a construction build or renovation in which we can view the entire build process coming together in a short video.
There are many different ways and workflows to create a time-lapse video. All that will effect the final look and outcome of the resulting video. From simply leaving a video camera running and then speeding up the footage to achieve this effect, to the more professional workflows of using dedicated photo cameras set to capture photo's or "frames" at a timed interval.
Here's a video that uses an array of evolved techniques to showcase the different possibilites based on the main concept of timelapse.
Professional timelapse workflows can get complicated fast, when it comes to setup, capture and post-production assembly. There are many considerations to make when it comes to interval math, digital memory considerations, framing for elements that don't exist yet, to keeping the capture rig safe and clear of problems during it's capture.
Long-Term timelapses complicate the process yet again as there are further considerations to deal with such as lighting changes, weather elements, and power considerations just to name a few.