Mutation strings

What are mutation stings?Read bout them somewhere

In what context ?

Mutation is something that mutates (changes), strings in relation to computers in general ‘a text string,’ strings in relation to virus detection are ‘signature strings,’ how a virus is detected.

So from that if it is in relation to virus detection it is a 'mutating/changing virus signature/string, this is done to attempt to avoid detection by convention signature based AV detection.