What's the difference between mutations, variants and strains?

Living through a global pandemic over the past year has seen virtually all Australians expanding their vocabularies in some way. 

But just when perhaps we thought we had a handle on most of the terminology, we’re faced with another set of new words: mutation, variant and strain.

So, what are their precise scientific meanings?

The genetic material of SARS-CoV-2 is ribonucleic acid (RNA).

To replicate, SARS-CoV-2 RNA hijacks a host cell and use the cell’s machinery to duplicate itself.