Kerbal Space Program

When playing an animation clip Unity offers several modes, Animation.Play() and Animation.Blend() are two of them, with the primary difference being that Blend() permits multiple animations to run on a gameobject at the same time, while Play() will stop any previously playing animations and frequently does so in weird ways.

More reading here:
http://docs.unity3d.com/ScriptReference/Animation.Play.html
http://docs.unity3d.com/ScriptReference/Animation.Blend.html

As an example, a lamp with adjustable focus, one animation activated the lamp and proceeds through a brightening curve, a second animation manipulates the range, brightness, and angle of the lamp. Using Play() to do this, the lamp would be able to turn on and off just fine, and you could manipulate it's focus just fine; but you could not manipulate it's focus while it's on, or turn it on while it's focus is at any value other than the starting position.

It's possible this analogy is flawed, the community will correct me if necessary.