Create a new .list file for a genome

Hello, 

How to create your own .list file (like hg38.list) based on the genome? 
I generated new genome_fasta_pileup_dir files using this command: 

> `BAFExtract -preprocess_FASTA  $genome.fasta .`

but I don't really get how to use this: `fetchChromSizes hg38 > hg38.list`
What exactly is hg38 here? 

Thank you so much for the reply in advance.