What is "Offset" in the fluid simulation "Bake" settings? I've only just recently started using blender (this is 2.78a) and am amazed at how much can be accomplished with it. I have been playing around with the fluid simulation, but all the different settings are a bit of a mystery, so I have a few questions, but I will start here with just one, and post others separately.

In trying to get multiple fluids to interact, I found that unfortunately, it is not possible, and the best one can get is: How to bake multiple fluid simulations in one scene?. However, in that answer, William Hopper mentions that to delay the start of the sim, one must change the "offset", but isn't that what "Time: Start" is for? What does each of these settings do?

My natural guess form the tooltip "Offset when reading baked cache" is so that one can have multiple baked domains in the same path, without having to do that workaround mentioned in the answer linked above.
This is pulled from another link on baking. 

Simulate objects falling into water

original answer by gandalf3♦

The Offset just "offsets" the frames that are being read from the cache. 

Time: Note that baking always starts on frame 1, these settings control the behavior of the fluid (e.g. for slow motion effects)

Start: The number of seconds into the simulation to start caching data.

End: The simulation time of the scene End frame in seconds.

Offset: Number of frames to offset reading of the cache. This is the only setting which you can still change after baking.