Point mutations are also considered single base modifications.
These are when a single nucleotide is either inserted, changed or taken from a ring of DNA or RNA. There are five different molecules that can make up nitrogenous bases on nucleotides and those are: cytosine, guanine, adenine, thymine, and uracil.
The difference between just a mutation and a point mutation:
Mutation- when a gene is altered through a change in DNA structure
Point Mutation- when just ONE nucleotide base is changed in some way
Hope this helps :)