The vaccines - differences?

Question

So pfizer and moderna are mRNA vaccines and Johnson’s is a live vaccine but not an mRNA vaccine? 
Can someone explain to me what this all means in a way that would make sense to a middle schooler please? 
Thanks!

Answer

J&J is NOT a live vaccine.  A live vaccine uses a weakened version of the virus that causes the illness.  It is a vector vaccine which means it uses a harmless virus as a vector. 
Neither vector nor mRNA vaccines contain any covid-19 virus.  
Both vector vaccines and mRNA vaccines contain instructions to teach your body to create the spike protein of covid-19 (essentially the recognizable 'face' of covid-19, but without the illness causing 'body').  When your immune system sees the 'face' it builds an immune response to it and remembers it.  This way if your body does get exposed to the actual virus, your immune system immediately recognizes it and already has the prebuilt tools to fight it off so it is unable to use your cells to replicate.

The vaccines - differences?

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