Mutations are any changes in the DNA sequence (nucleotide sequence), that can be inherited to the next generation. It can be spontaneous or induced. Spontaneous ones are caused due to errors in DNA replication. Induced mutation is caused due to physical or chemical mutagens. If mutations occur in coding regions of the DNA that can alter the organism's phenotype.
Evolution is a change produced in the species as a long term or gradual process. It happens to survive in an environment full of competition. Darwin's theory of "Survival Of The Fittest " explains this precisely.
Mutations that are not lethal serve as a basis for evolution.
