The Human Genome Project was an international research project to find all the nucleotide base pairs that make up human DNA, and to map all human genes to understand what they code for.
This project lasted from 1990 to April 2003.
Using DNA samples from volunteers (whose identities are kept secret to protect their privacy), scientists sequenced (determined the exact order of the base pairs in DNA) an entire human genome (a complete set of DNA).
Obviously, the DNA sequenced from the sample is not the same for every human. But it helped scientists better understand genes and figure out where genes were located, what base pairs coded for specific alleles of genes, etc.
All information found in this study, including the sequenced genome itself, is public and can be accessed by anybody.