Lymphoma is a type of sickness that happens inside our bodies. It is a kind of cancer, which means it is a very serious illness. Lymphoma specifically affects a part of our body called the lymphatic system. This system is like a big network of roads inside us that help carry a special fluid called lymph around. When someone has lymphoma, they have a problem with the cells in their lymphatic system that start to grow in an abnormal way. This can make them feel sick and cause different problems in their body. Doctors and scientists are working hard to find ways to help people with lymphoma get better.