Conjunctions are the all-important 'joining' words that connect different phrases together. Without conjunctions, it would be impossible to understand language itself. You couldn't answer where anything is. You couldn't explain how to use anything. Even telling the simplest story becomes impossible without conjunctions.
Wars have been declared over a single incorrect conjunction.*
--caption 'Which is it? That seems like a pretty crucial conjunction...'--
This is why learning the correct conjuction to use is vitally important in any language in which you wish to become skilled.
'On' is the worst offender in our modern world. People (even native speakers) seem to think that 'on' can be substituted for any conjunction, when coming up with the right one is too hard.
At R.Story, we specialize in the highest form of 'correct' everyday speech. You won't sound like an old dictionary, but you won't sound like an internet celebrity either. We believe that this high standard of communicative English is still in demand in the professional world.
*(Probably. We don't really know. Our whole world is apparently explained to us by Wikipedia.)