Genome is the entire genetic material of an organism.
Sequencing a genome is working out the DNA base sequences for all the DNA is a cell.
Easier to sequence the DNA of simple organisms (prokaryotes) since there are no introns an the genome directly used to sequence the proteins that derive from genetic code (proteome) so you can use the potential antigens to produce a vaccine.
Eukaryotic organisms have introns and regulatory genes so genome cannot be used to translate the proteome.