Which does the phase ''to agree to disagree " mean

It means you can say you agree to whatever someone is saying just to stop them from talking but in your opinion you disagree completely to what their saying.

The term "agree to disagree" or "agreeing to disagree" is a phrase in English referring to the resolution of a conflict  where by all parties tolerate but do not accept the opposing position(s).

Let me give you an example:
If say that the sea is blue-ish and you say its green-ish. Neither of us are prepared to alter our belief, so we agree to disagree.
I hope it helped!! :)

Scientific Method...