1) The document discusses de Bruijn graphs and how they can be constructed and used to represent relationships between multiple genomes without the use of a reference genome. 2) De Bruijn graphs are built by using every unique k-mer as a node and connecting nodes that share a k-1 overlap. This implicitly captures overlaps between sequences. 3) The graphs can be used to analyze similarities and differences between many genomes at once and investigate phylogenetic relationships.