TILs therapy involves extracting tumor-infiltrating lymphocytes (TILs), which are the most precise natural anti-tumor immune cells in the patient's body, from a tumor and cultivating them in large numbers in a lab. These activated TILs are then reintroduced into the patient's body to bolster the immune system's ability to target and kill cancer cells. TILs work by recognizing specific markers on cancer cells and launching an immune response against them, ultimately leading to tumor destruction.