Okay kiddo, so in 2011, something really scary happened to the British Embassy in Iran. There were a bunch of people who didn't like the British, and they wanted to hurt them. So, they broke into the embassy and started throwing things and breaking stuff.
This is called an "attack" because the people who did it wanted to cause harm to the people inside the embassy. It's kind of like when someone tries to hurt you on the playground - it's not very nice.
The people who did the attack were really angry because they thought the British were treating Iran badly. They didn't like some of the things the British government had done, so they wanted to show them how upset they were.
Luckily, no one was hurt too badly in the attack, but it was still a scary thing for the people who were there. They had to be really brave and stay calm until help came to get them out of there. It's important to remember that violence isn't the answer to problems, and that there are better ways to solve disagreements than hurting other people.