questions I need answered

1. What is being "triggered" mean? I see trigger warning on here and idk what it means 
2. Did Colin K actually sit on his bum during the anthem or did he take a knee? I'm confused on why it's a big deal if he took a knee because that's considered sign of respect for fallen comrades. You always take a knee during injury / ect? 
3. Yeah that's it I'm sorry I'm dumb I'm new here & your girl needs help 🙄