What's your favorite domestic website? Why?

The website I use most often is EdX. EdX originated from a network project founded by MIT and Harvard University, and its ambition is to educate billions of people around the world. Since its establishment, 25 key universities around the world have joined the program. The website is open to everyone, and you can enjoy quality education courses with only one login account. I personally like this website. Now many courses are published in Chinese, so you can go and have a look.