whats mean of ll -lart and ll -alrt ?
ll is an alias for "ls" - type
man ls
and check out the switches. Both your commands should show the same result, because in most cases the order of switches or concatenating them doesn't matter.
from the manuals:
-a, --all
do not hide entries starting with .
-l use a long listing format
-r, --reverse
reverse order while sorting
-t sort by modification time
The alias ll is by no means standard, although some Linux distros for example have it in their default configuration.