I don't really understand what fold mean means

Question

[ManuelDB]

What 198-fold mean means in the following sentence:

Typically, only a small fraction of a genome has 'low' relative coverage. For example, 198-fold mean coverage of the human genome by Illumina HiSeq 2000 version 2 chemistry only left 0.23% of bases undercovered by a factor of 10 or more (data set A2). At first glance, this portion of the genome appears minuscule, but if the data were unbiased, we would expect no bases to have such a low level of coverage (more than 12 standard deviations less than the mean)

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4053816/

Answer 1

[Trivas]

it's 198-fold mean coverage. Not clear from that exerpt what it's comparing it to, but the mean coverage in one sample is 198-fold higher than a different sample.

[GenoMax]

From the linked paper