Hi, I am working with DNA sequencing libraries, although this question could serve as well for RNA-sequencing. Adaptors and random hexamers can be both used in a same library? Are both referring to the same thing? And this is what we normally see in the Per Base Sequence Content, in the first positions of the plot?

What is the function of each one if not? I thought both are used to serve as DNA primers and help the polymerase action? Thanks!