It was an ordinary track suit in the 2000s-2010s. Tracksuits like this are often a part of school uniforms in Asia.
Actor Wu Jing played a physical education teacher in 2019 movie Song of Youth wearing a green tracksuit with "China" (中国) in giant characters. Wu Jing has been the lead actor for several patriotic-themed action movies, and a screenshot of him wearing a green tracksuit with China in giant characters has become one of the hottest memes on the Chinese internet in 2021. There's even a term for memes featuring Wu Jing, called "Jing Memes" (京图).
The meme has further spread after people started photoshopping words onto that screenshot, forming phrases with the word "china" (or "chinese" depending on the context) in it. Such as "Mosquitoes fk off of CHINA" and "Failed to lose weight, I blame CHINESE food for being too delicious". Especially during the Tokyo Olympics, where the meme had a blast on Olympic related edits.
Genshin Impact did a parodyof this with a short film in August 2021 featuring an actor wearing a sports jacket with "Liyue" (the nation in Genshin that's based on China) written on it. This meme is known to Genshin players all over the world. They also later started to sell merch of this tracksuit.
