What is confidence goal in an experiment?

Confidence Value or Confidence Goal is a measure of the reliability of an estimate, typically written in the following form of a percentage: 95.0%

Let’s suppose you performed an experiment between two landing pages. As the experiment starts, we will start getting the visits and conversions data for each of the landing pages. Now lets say Landing Page A performs better than the other based on the conversion rate. But it will be incorrect to decide that A is the winner  based on the initial data. This is where the confidence value comes into picture.

Whenever we find a better landing page we need to state what is the confidence in that calculation. Usually its recommended to wait for a confidence of minimum of 95% before declaring a winner.