I cannot understand the purpose of this phrase "tun und lassen", I saw it in sentence like this:

Das ist mein Auto. Ich kann damit tun und lassen, was ich will!

Translation in English (deepl.com):

This is my car. I can do what I want with it!

But if I change the sentence:

Das ist mein Auto. Ich kann damit tun, was ich will!

Translation in English (deepl.com):

This is my car. I can do what I want with it!

There is no change in the translation. I have tried other translators, same result.

In dict.cc it says that "Tun und Lassen" is idiom and it translates to "all sb.'s doings", but that makes no sense.

Is it used to emphasize something?