Master Tang is right.
Think of it like this.
Volume shows traders/investors interest in the market.
If the market has made a new high and is high in volume, that suggest traders are interested in this new high and are buying into it. If it made a new high and was very low in volume that would suggest uncertainty or no interest.
Volume alone won’t cut it though. Just like any other indicator it should be used in conjunction with other methods. There have been many times i have entered a breakout successfully when the volume didn’t spike.