Difference between LSP and CodeIntel

I would like to know the difference between using LSP and CodeIntel, because if I know it then it would be easy for me to choose which one to use in which work environment.

Also I would like to know is it possible to use both at the same time.

Are both equal or have slight difference in different scopes like one if better in Auto completion that the other so that I can have a configuration where I disable weaker features and enable better feature.

"Just out of Curiosity"