Okay, so you know how in some stories or movies, the hero or main character has to carry something really heavy, like a big rock or a bucket of water? Well, in a very old story from a really important book called the Bible, there is a man named Jesus who had to do something like that too.
Jesus was a very special person who tried to teach people about being kind and loving to each other. But some of the other people in charge didn't like what he was saying, so they arrested him and made him carry a big wooden cross through the town to a place called Golgotha.
Now, this wooden cross was not only really heavy, but it also hurt a lot because it had sharp nails sticking out of it that poked into Jesus' skin. So, Jesus had to carry this heavy, painful thing all the way through town, while people were shouting mean things at him and even hitting him.
But Jesus did it anyway because he wanted to show people how much he loved them, even when they were being mean to him. And even though it was really hard, he never gave up because he knew that what he was doing was important.
So, when people talk about "Christ carrying the cross," they are remembering this story about Jesus and how he showed us all what it means to be strong and loving, even when things are really hard.