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Tech Fundamentals — The 6 Core Concepts Behind Building Applications

This video covers six foundational technology concepts you need to understand before we start building. You don't need to master the technical details — Claude Code handles most of that now — but understanding how these pieces connect will make you a significantly better prompter and builder.

1. APIs (Application Programming Interfaces): An API is how applications talk to each other. Think of it like a waiter in a restaurant — you (the client) place an order, the waiter (the API) carries it to the kitchen (the server), and brings the result back. Every major service — Stripe, GitHub, Xero — has an API so that external apps can send requests and receive data. When we send an API request, we're making an HTTP request to a specific URL (called an endpoint). The main request types are GET (retrieve data), POST (create data), PUT (update data), and DELETE (remove data). Each request can include headers (like authentication keys to prove who you are), a body (the actual data you're sending), and parameters (variables like dates, amounts, or currencies). For example, to create a payment link via Stripe's API, you'd send a POST request to their endpoint with the amount, currency, and your API key in the header.

2. Authentication & API Keys: API keys are essentially passwords that prove you're authorised to access a service. If you're paying for Claude's API or Stripe, they give you a unique key so nobody else can use your account. Key rules: never share them publicly, never commit them to GitHub, and store them securely in a .env file on your local machine. Leaked API keys mean other people use your account and you pay for it.

3. Front End vs Back End: The front end is everything you see in the browser — buttons, text, design, layout. It's built with HTML (structure), CSS (styling), and JavaScript (dynamic actions like button clicks). The back end is where the logic happens on a server. When you log into Stripe, the front end shows the login form, but when you hit "sign in," a request is sent to Stripe's server to check whether your email and password match a real account. That validation happens on the back end because your credentials are stored securely on their server — not on your local computer. The server sends back either an approval or a rejection, and the front end responds accordingly.

4. Full Stack, Hosting & The Cloud: Full stack means front end + back end + database — the three core components of any application. Your own computer can act as a server (localhost), but if you turn it off, everything goes offline. That's why companies like Amazon (AWS), Google, and Microsoft built massive server farms you can rent — that's "the cloud." You only pay for what you use, it runs 24/7, and it scales up or down as needed. Our tech stack for this course: Next.js (front end), Supabase (database and auth), Vercel (cloud deployment), and Claude (AI). When building locally, you'll use localhost:3000 — only visible on your machine. To make an app publicly accessible, you deploy it to the cloud at a public URL. Environment variables (.env files) store your API keys locally and should never be pushed to GitHub. CI/CD (Continuous Integration/Continuous Deployment) is the workflow for pushing code to GitHub and publishing it to the web — you'll see exactly how this works when we build.

5. JSON & Data Formatting: JSON is a way of structuring data using key-value pairs — like "firstName": "Adam" or "age": 30. It makes data easy to search, index, and reference in code. Instead of writing a paragraph about yourself, JSON lets you store each piece of information with a clear label so functions can look up exactly what they need. Syntax matters — a missing comma or misplaced apostrophe will break everything. The good news is AI models almost never make syntax errors, but back in the day, developers would spend hours hunting down a single missing character.

6. Webhooks: Webhooks are a more efficient version of API polling. Instead of repeatedly asking a service "are you done yet?" every few minutes, you give them a URL and say "send me the result here when you're finished." A real-world example: you sell football boots through Stripe and want to send a thank-you email after every purchase. Instead of checking Stripe every five minutes for new payments, you set up a webhook — Stripe automatically sends a request to your API whenever a checkout completes, triggering your email function instantly. Webhook security matters too — you need to verify that incoming requests are actually from Stripe and not a bad actor pretending to be Stripe, using signature verification and authentication tokens.

Bonus — LLMs (Large Language Models): LLMs like Claude, ChatGPT, Gemini, and Llama are neural networks trained on massive datasets. They all perform differently and have different pricing, context windows, and strengths. We'll primarily use Claude, but may use OpenAI or Gemini for specific tasks (Gemini is strong for image/video generation, Llama is open source and can run locally for free). Pricing is based on tokens — roughly equivalent to characters — charged per input and output. The $20/month Claude plan is more than enough for most personal use cases.

The Big Takeaway: You could spend 30+ hours going deep on each of these topics, but with Claude Code and AI coding, understanding line-by-line technical detail is no longer critical. What matters is understanding the fundamentals and how they connect. The fastest way to learn is to start building — and whenever you have a question about what the AI is doing, just ask it. You have the equivalent of the world's top universities accessible in seconds. Theory sets the foundation, but building is where it clicks.