1. ESM has to explicitly specify file extension in import statement; but file extensions are totally optional with the CommonJS require function.
2. ESM modules run in strict mode and cann't be disabled.
3. ESM doesn't define references avaliable in CommonJS, including require, exports, module.exports, __filename and __dirname. But following code shows alternative solutions.

import { fileURLToPath } from "url";
import { dirname } from "path";
import { createRequire } from "module";

// import.meta.url is the reference to the current module file in a format
// similar to file:///path/to/current_module.js.
const require = createRequire(import.meta.url);
const __filename = fileURLToPath(import.meta.url);
const __dirname = dirname(__filename);

4. In the global scope, keyword this is undefined in ESM; but this equals to exports in CommonJS.
5. At runtime, ESM uses built-in function import() for loading modules; and require() for CommonJS.
6. ESM has ability to load CommonJS modules by using function module.createRequire() or statement import...from...; CommonJS can't load ESM modules. Note: statement import can only work for default exports of CommonJS.
7. ESM cannot import JSON files directly as modules, but module.createRequire() still works for this limitation, just like importing CommonJS module:

import { createRequire } from "module";
const require = createRequire(import.meta.url);
const data = require("./data.json");
console.log(data);

The resolving algorithm can be divided into three major braches:

1. File modules: If module name starts with '/' or './', it will be considered as absolute or relative file path;
2. Core modules: Against point 1, module name will be considered as pointing to someone mudule, and first try to search within the core Node.js modules;
3. Package modules: Against point 1 and 2, or no core module matched the name, then the search continues by looking for a matching module in the first node_modules directory that is found navigating up in the directly structure starting from the requiring module. And continues to search for a match by looking into the next node_modules directory up in the directory tree, unit it reaches the root of the filesystem.

Additionally, for file and package modules, both files and directories can match the moduleName. In particular, the algorithm will try to match as following:

1. <moduleName>.js
2. <moduleName>/index.js
3. The directory/file specified in the main property of <moduleName>/package.json