Little
The word " little " emphasis on the lack of something.
For example
We have little money right now. We should go out for dinner some other time.
The statement tells us that we should be careful and use the money wisely because there is not much left.
A Little
"A little" emphasis that something still remains.
For example
There's a little ice cream left, who will eat it?
This statement tells that there's not enough ice cream to save it or put it back in the freezer so it should be eaten.