when using react with express, is that SSR or static or SPA?

Question

This is my server.js file.

const express = require('express');
const connectDB = require('./config/db');
const path = require('path');

const app = express();

// Connect Database
connectDB();

// Init Middleware
app.use(express.json({ extended: false }));

// Define Routes
app.use('/api/users', require('./routes/users'));
app.use('/api/auth', require('./routes/auth'));
app.use('/api/contacts', require('./routes/contacts'));

// Serve static assets in production
if (process.env.NODE_ENV === 'production') {
  // Set static folder
  app.use(express.static('client/build'));

  app.get('*', (req, res) =>
    res.sendFile(path.resolve(__dirname, 'client', 'build', 'index.html'))
  );
}

const PORT = process.env.PORT || 5000;

app.listen(PORT, () => console.log(`Server started on port ${PORT}`));

Since we npm run build, isn't that a static file? (for ex, when we deploy to heroku and it builds after deployment).

This is from my package.json file.

"scripts": {
    "start": "node server.js",
    "server": "nodemon server.js",
    "client": "npm start --prefix client",
    "clientinstall": "npm install --prefix client",
    "dev": "concurrently \"npm run server\" \"npm run client\"",
    "heroku-postbuild": "NPM_CONFIG_PRODUCTION=false npm install --prefix client && npm run build --prefix client"
  },

How about when we use react router vs express routing? Is that still static since it's all built at deployment?

BTW, all this code is from Brad Traversy's React Front To Back course.