In recent years, more and more public gaming spaces like conventions and game shops have been introducing the X Card. The X Card can be a physical card or a hand signal, but what it indicates is “I am not comfortable with what’s happening.” Either a player will tap the card, or do the hand signal, and then the DM and other players will move away from whatever was being described at that moment.
Another card that’s not as commonly used, but is gaining popularity, is the O card. The O card (or hand signal) functions the same way as the X card but has a different purpose. When a player taps the O card (or does the hand signal), they are indicating that they are OK but that they are edging towards being uncomfortable.
Because of their efficiency and simplicity, X/O cards are most effective for public games where you might not get a chance to know the DM or other players, and maybe wouldn’t want those people to know your deepest phobias or triggers. Some argue that regular use of X/O cards can slow down a game, or allow players to be ultra-sensitive or dictate the game narrative. Like any tool though, it is the onus of the DM to educate their players about how and when to use the cards to ensure that the system isn’t abused or misused.
And like anything else in D&D, there is no catchall solution for every table and player and DM. Now that you understand the premise of why safety tools exist, think about what you can do at your table to make sure everyone is feeling comfortable and enjoying themselves. If none of these tools work for you, talk to the other players at your table to come up with a solution that suits your style. After all, if your characters can conspire together to steal a priceless gem from a dungeon, you can probably figure out a way to facilitate effective communication and teamwork outside of game too.