Yes and no at the same time.

Film is actually more sensitive than a sensor is and the sensor at 400 is an approximation of films sensitivity...not what I would call accurate in all manners but close enough for our purposes.

One thing with film though is that you many times use a faster fil in order to get a certain grain or texture from the image. With digital sensors though this grain is instead what is called "noise" and is useless as a desired feature.

This is one reason why film will always be superior to digital you can get grain and you can do it in camera instead of in PS.

 

It is how sensitive to light you want your camera to be. The higher the ISO, the more sensitive it is. It kinda translate to a few different things when applying it to different scenarios.