You can customize this space however you like:
Edit files in /var/www/html/ to serve static content.
Start any web server on port 3000 and it will be automatically proxied:
# Node.js example
cd /home/node/app
npm init -y
npm install express
node server.js # listening on port 3000
# Python example
cd /home/node/app
python3 -m http.server 3000
Your app files are in /home/node/app/