Electro-Rock/Electronic Rock

I always assumed Electronica and Electronic-Rock was two entirely different things.

Well, the way that I look at it, "electronic-rock" doesn't even exist. There's electronic, and then there's electronica. Electronic music refers to music that emphasizes the use of electronic musical instruments (and nothing else) as a central aspect of the sound of the music.

Electronica is different. You might even say that it's "everything else". It's designed for a wide range of uses, like foreground listening, some forms of dancing, and background music for other activities; but unlike electronic dance music, it is not specifically made for dancing. You know how pop has subgenres, like dance-pop, piano-pop, etc? Electronica is just a subgenre of electronic music.