Can someone explain the WTA to me like I’m 5?

This is my first wta finals and I’m so confused on how it works. Amanda just lost to Elena so I thought she would be out, but I just checked the schedule that shows she’s playing Madison on Monday. I’m so confused, how are they still in? Does this mean they still have a chance of winning the whole thing? How does one move on to the semi finals/finals? I feel so dumb for asking this question because I still didn’t understand when I asked chat GPT lol. Any kind people want to dumb it down for me? 😂