First you need to figure out what a virus is.
A virus can be said to be a special form of existence of matter that can only be reproduced inside living cells ( plants, animals, even bacteria) That is, the virus multiplies in the cells of other organisms.
Coronaviruses are a whole family of viruses that unites similar species. The name comes from the presence of crown-like spines in them.
There are strains (varieties), and previously there were outbreaks of coronavirus infection in 2002, 2015.
The new strain was named SARS-CoV-2, it is the causative agent of SARS.
Most likely, bats (bats) became carriers of the virus, which bit other animals, which were then sold at the local market in the city of Wuhan, where unsanitary conditions prevail, which led to the rapid spread of the virus.
There are many conspiracy theories that the virus was created artificially for the purpose of being used as a biological weapon.