You built a two-node workflow in the last guide. Every workflow you'll ever build in n8n - two nodes or two hundred - is made from the same handful of node categories. Once these click, reading (and building) any workflow gets a lot faster.
What a node actually is
A node is one step: do this one thing, with this configuration, to whatever data arrives. Under the hood, most nodes are thin wrappers around an API call - the Gmail node calls Gmail's API, the Slack node calls Slack's API - configured through a form instead of raw code. That's the whole trick: n8n gives you hundreds of pre-built API wrappers so you rarely have to read API documentation yourself.
The main node categories
Trigger nodes start a workflow. Every workflow needs exactly one active trigger (with a few advanced exceptions). Common types: Manual Trigger (click to run, covered in the last guide), Schedule Trigger (run every hour, every Monday, etc.), Webhook (run when an external system sends a request - covered in a later guide), and app-specific triggers like "new email" or "new row added."
Action nodes do the actual work: send a Slack message, update a spreadsheet row, call an API, transform data. Most of a workflow is action nodes chained together.
Logic nodes control flow without calling any external app: IF branches based on a condition, Switch branches into more than two paths, Merge combines data from two branches back into one, and Loop Over Items processes a list one chunk at a time.
Code nodes are the escape hatch mentioned in the first guide - a JavaScript or Python node you can drop in anywhere the built-in nodes don't quite do what you need.
Picking the right trigger
This is the decision that shapes everything else about a workflow. Use Schedule Trigger for anything time-based - a daily report, a weekly cleanup job. Use a Webhook when another system needs to notify n8n the instant something happens - a new form submission, a payment event. Use an app trigger (Gmail, Airtable, Google Sheets, etc.) when you want n8n to poll or listen to a specific app for changes, without building the webhook plumbing yourself.
Reading a node's three tabs
Click into any node and you'll see three areas: Parameters (the configuration - what you fill in), Input (the data this node received from whatever ran before it), and Output (the data this node produced, after it ran). Getting comfortable clicking between Input and Output on a node you're debugging is probably the single highest-leverage habit in learning n8n - it's how you actually see what's happening instead of guessing.