Heroic 4’s are quests you can do in a group of 4 players or less. Because completing Heroics give you a lot of experience points (for leveling) and better loot (gear) than in solo quests, people call out in general chat to check if anyone else is interested in joining your group.

When you /Say, only people in your character’s vicinity can read what you wrote. When you /1 or /General, everyone on the planet (in my case, Alderaan) can see what you wrote. This was my first time looking for a group (LFG) and I…happened to not know there was a difference between general chat & /say.