Yellow alert means weapons aren’t armed but shields are. Red alert means weapons are energized. You might go to yellow alert for an unknown anomaly or a ship in distress. Something that would require the crew to be ready for some shit popping off but not high alert for combat.
The difference is more of a posture thing. You don’t walk up to someone in distress with your fists up but you might approach with caution in case it’s a trap. Same for yellow/red alert. Other ships can scan you and see when you’ve got your weapons armed. If you come warping in to help someone with gun ports bristling they might take you as a threat instead of as help.
Yellow alert means weapons aren’t armed but shields are. Red alert means weapons are energized. You might go to yellow alert for an unknown anomaly or a ship in distress. Something that would require the crew to be ready for some shit popping off but not high alert for combat.
Now you see if theres a threat that requires shields then it natually means you should have someone on weapons as well. Which means its a red alert.
I got bored after my last comment and looked it up:
https://www.overthinkingit.com/2012/10/22/star-trek-the-next-generation-red-alert/
Its not even used in the show that much
The difference is more of a posture thing. You don’t walk up to someone in distress with your fists up but you might approach with caution in case it’s a trap. Same for yellow/red alert. Other ships can scan you and see when you’ve got your weapons armed. If you come warping in to help someone with gun ports bristling they might take you as a threat instead of as help.
Also if you are investigating one of those exploding nebulas phasers aren’t gonna help but shields might