Random hexameters and adaptors are the same thing?

Question

[CL]

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!

[ATpoint]

Random hexamers for cDNA synthesis : https://en.wikipedia.org/wiki/Complementary_DNA

Adapter ligation for NGS libraries: https://international.neb.com/applications/ngs-sample-prep-and-target-enrichment/dna-library-preparation

fastqc per base bias: https://www.bioinformatics.babraham.ac.uk/projects/fastqc/Help/3 Analysis Modules/4 Per Base Sequence Content.html

It's worth noting that some types of library will always produce biased sequence composition, normally at the start of the read. Libraries produced by priming using random hexamers (including nearly all RNA-Seq libraries) ...