So, because I want to, let's discuss terminology. I'm not saying that I'm the final source of truth in this--we've all heard it different ways--I'm just going to say what I've found in my research to be the most common use of the term.
Inciting Incident: This is the event that makes this day (where your story begins) different than any other day. The event that changes your MC's life, even though they may not know it yet.
Quick movie reference: Tangled, inciting incident is when Flynn Ryder shows up in Rapunzel's tower.
Key Event: This is when the MC begins to actively participate by making a choice that thrusts him/her into the action. When the MC becomes engaged in the story, usually because of the inciting incident.
The key event is often called the inciting incident, along with various other names. This is why there is so much confusion.
Quick movie reference: Tangled, key event is when Rapunzel decides to leave the tower and forces Flynn to help her.
Can the inciting incident and key event be the same? Yes, occasionally they can.
Does it really matter what term I use for them? No, but it's important to understand that both are an important part of story telling.