What is Eigengene value? how they can be calculated for groups of genes in two conditions? How SVD is related to it?

Question

[m.sadman.sakib]

I have a very basic and naive question. What is meant by eigengene? I have a group of gene expression value in in my control vs mutant plant from RNAseq data. I somehow want to plot the overall gene expression of all those genes in control vs mutant. Naive way would be to take the average of normalized gene expression values of those genes and plotting them. But I was looking for more sophisticated way to do that. My googling led me to terminology like "eigengene" or "single value decomposition". Are they similar in concept? Can one suggest how I can solve this problem?

Best, John