Histones are positively charged proteins rich in basic amino acid residues, lysines, and arginines. These proteins bind around 200bp of negatively charged DNA into large loops to form a nucleosome.
It is the non-nucleosomal DNA connecting two or more nucleosomes in a formation. Linker DNA length ranges between ~20–90 bp, giving the appearance of a string of beads.
DNA is the hereditary material in humans. But human DNA is almost two meters long and will not fit into the cell's nucleus. Therefore, this DNA is condensed by packaging it with proteins.