Okay kiddo, the Cold War was a time between two big countries - the United States and the Soviet Union (which was called Russia back then). These two countries didn't like each other very much and were always afraid of the other one attacking them.
Canada was friends with the United States and they were on the same side, so they both wanted to make sure they were prepared in case Russia decided to attack. This time was called the Cold War because even though the two countries didn't actually fight, they were always super worried and scared about what might happen.
Canada was important during this time because it was right in the middle of the two big countries. This meant that Canada was a sort of buffer between the United States and Russia, and it was important to make sure that neither country could attack the other through Canada.
Canada had to be very careful during this time to stay on the good side of both the United States and Russia. They made sure to have good relationships with both countries, while also making sure they were prepared for any attacks. They did things like building military bases, testing weapons, and training soldiers to make sure they were ready.
Overall, Canada played an important role during the Cold War by helping to keep the peace and making sure that they were prepared in case anything bad happened.