The background is the "universe" of all genes, from which a list of genes of interest was obtained. For microarrays, these are all genes on the array, for RNA-seq, these are all genes, often subsetted to protein-coding transcripts. See "14 - Functional enrichment analysis" section here mdozmorov.github.io/BIOS567.2017/syllabus/ for more details on the topic of enrichment.
Thank you! Very helpful!
Background means what exactly?
The background is the "universe" of all genes, from which a list of genes of interest was obtained. For microarrays, these are all genes on the array, for RNA-seq, these are all genes, often subsetted to protein-coding transcripts. See "14 - Functional enrichment analysis" section here mdozmorov.github.io/BIOS567.2017/syllabus/ for more details on the topic of enrichment.