You always get mutations because nature isn't perfect, and organisms are complicated. The genetic code accounts for that so that if you get a single point mutation, the probability that it still codes for the same or a similar amino acid is quite high.
That means the protein it codes for can probably still function, which is all nature cares about.
There isn't really a significance. There are 20 "ancestral" amino-acids, while the genetic code uses triplets from 4 distinct nucleo-bases (ACGT) which yields 64 codons. Redundancy is unavoidable.
Now, why did the genetic code evolve based on triplets... that's kind of a million dollar question
However, there are significant or interesting properties and consequences of redundancy. Maybe this was the question you had in mind?
alsokalli t1_j9g9x3i wrote
You always get mutations because nature isn't perfect, and organisms are complicated. The genetic code accounts for that so that if you get a single point mutation, the probability that it still codes for the same or a similar amino acid is quite high. That means the protein it codes for can probably still function, which is all nature cares about.
(This is very, very simplified)