what does "ls'" mean in Linux?

I accidentaly typed ls' and I got a interactive interface: > What is this?

I tried search on internet, found nothing.

This behavior is distro agnostic. You had open a quote, the shell is displaying $PS2 global variable ($PS2 is the > in your output) while the second quote is missing.

You can change PS2 with what you want instead :

Ex: export PS2=">>>"

The value of $PS2 is printed (after expansion) as the secondary prompt for more data when bash is running interactive. See man bash, under PROMPTING.

-bash-4.1$ ls'
>

it means that you open a long string with ' and didn't close it so bash is waiting for string(argument) ended with '

Use ls without any ' at the end.