What is npm and how does it work with Node.js?

Direct answer

npm (Node Package Manager) installs JavaScript packages into node_modules, records semver ranges in package.json, and runs scripts — it ships with Node and powers the largest open-source registry for server and tooling dependencies.

npm is both a CLI tool and a registry. Monorepos like AceDevHub use npm workspaces so apps/api and apps/web share lockfile integrity from the repo root.

Command	Purpose
npm install	Install deps from package-lock.json
npm install fastify	Add runtime dependency
npm install -D vitest	Add devDependency
npm run dev	Execute scripts.dev from package.json
npm ci	Clean install for CI — fails if lock out of sync

node_modules — nested dependency tree; lockfile pins exact versions for reproducible builds.
semver — ^1.2.3 allows minor/patch; exact pins for critical prod (Q41).
Alternatives — pnpm (content-addressable), yarn — same registry, different install strategy.

package.json-snippet.json

{
  "name": "@acedevhub/api",
  "scripts": {
    "dev": "tsx watch src/index.ts",
    "content:import:interviews": "tsx src/scripts/import-content-interviews.ts"
  },
  "dependencies": {
    "fastify": "^5.0.0",
    "pg": "^8.13.0"
  },
  "devDependencies": {
    "tsx": "^4.19.0"
  }
}