# Nodes and execution
### The anatomy of a node
A node represents an **instance** of a function or event, with the original function or event being its **declaration**. Each node has input and output properties, as well as input and output triggers. Properties handle data acceptance and production, while triggers determine when a node is called.
Nodes without triggers are called on demand.
### Execution order
Understanding the difference between triggers and properties is crucial. Properties pull data from their connected sources, while triggers pushes the flow of execution to the next trigger.
#### Example of execution order
1. When a request is received matching the `/hello` endpoint with method `GET` and a query parameter `name`, the `HttpEndpoint` event is triggered.
2. The `Template` node is then called, because the `Log` node depends on its result, and it doesn't have any triggers.
3. The `Log` node is executed, with input from the `Template` node.
4. The `Template` node is called again, since the `HttpResponse` node also depends on it.
5. The `HttpResponse` node is called with input from the `Template` node.
#### Functions without triggers
Functions without any trigger inputs or outputs are called **on demand**, and don't cache their results, meaning that if several nodes depend on the output of a single non-triggerable node, it is called several times, like in the example above.
Functions with triggers can only be called by triggering them from a previous function or event, or by clicking the **play**-button in their header.
They do **cache** their results, meaning that as long as a triggered node has been called, any node that depends on any of its outputs will use the values from its last execution.
{% hint style="warning" %}
If a node depends on value from a triggered node which has not yet been called, the result will be `null`.
{% endhint %}
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