explain shell

I just got to know this website from twitter explain shell
It is very useful, especially when I have a complex linux command and can not figure out what
does each flag mean.

For example:  du -h -d 1 ~

This command is very useful to check the folder sizes.
you can sort the folder by size:

tommy@tommy-ThinkPad-T420:~$ du -h -d 1 | sort -hr
63G .
16G ./homer
14G ./Desktop
13G ./Downloads
3.3G ./MochiView_v1.46
1.9G ./anaconda
1.2G ./scientific_writing
1022M ./.cache
938M ./SeqMonk
845M ./mochi_view
625M ./jorg_bungert
587M ./.thunderbird
400M ./.local
379M ./R
331M ./Datasets
257M ./gatk-protected

........