Variants of viruses are common. It is merely a replication of the original virus. In other words – the virus makes a copy of itself and sometimes ‘makes a mistake with the copying process’. As the virus mutates, it doesn’t always make an exact copy of itself (as simplified above).
We can clearly see the difference (and resemblance) above. As the virus changes and makes a copy of itself, it often doesn’t always get the exact ‘copying procedure’ correct. This results in a different ‘appearance’ called a mutation. Therefore any virus with one or more mutation are sometimes called variants.
Lets look at how the Covid-19 Virus has mutated:
a) Alpha Variant (previously called B.1.1.7 First identified in the UK)
b) Beta Variant (previously called B.1.351 First identified in S.A.)
c) Gamma Variant (previously called P1 First identified in Brazil)
d) Delta Variant (previously called B.1.617 First identified in India)
Think of the common flu. Every year it changes. Thats why doctors recommend and apply different flu vaccines every year to accommodate the current strain.