Tab completion and electric-indent-mode

[carlmarcos]

Have been delving into tab completion and encountered the variable 
`tab-always-indent` where I can use the tab key for completion at point.    
Does there exist any relationship between the variable `tab-always-indent` and 
`electric-indent-mode`?

Would `(setq tab-always-indent 'complete)` interfere with any functionality 
that one would usually want to have?
 
`electric-indent-mode` says that in does "On-the-fly Reindentation".  What does 
that mean, and how is it different to normal indentation?