# Node Connections

There are several types of connections between nodes, but there is one that is special. It is called **Lifeline**.

It is the one with a lime color and it determines the action flow of the layout. Contrary to most other connection types, an input pin can have many connections whereas an output pin can have only one.

*Layer layouts* consist of nodes connected with chains. There are **2 types of chains:**

* **lifeline chain** and a
* **sub-chain**.

## Lifeline chain

It consists of nodes connected with a lifeline connection. It is shown with a lime green color and has square pins.

![A lifeline chain with nodes labeled as per the order of execution.](/files/BbEwbfF94v2J3Z9AgPYg)

{% hint style="info" %}
**Good to know:** One lifeline output can be connected to only one lifeline input, but one lifeline input can be connected to several lifeline outputs.
{% endhint %}

## Sub-chains

It consists of all the nodes that are connected with other connection types, but if they are to be executed, their *sub-chain* needs to be connected to the *lifeline chain*.

![All non-lifeline connections above are a sub-chain of the one lifeline connection.](/files/kZWRTSTzpri0bEvM0JpE)

Connections between nodes have different colors. Each color represents what is sent along that connection. For example, dark red represents a float which stands for a *real number* whereas light blue represents a string or text.

{% hint style="info" %}
**Good to know:** You can only connect pins with the same color and you can only connect an output to an input.
{% endhint %}

## Active vs Inactive connections

A connection will be **active** or enabled only when the **Playhead** on the Section is placed *on top of a layer* and only when it is connected to a lifeline generator in some way.

![Example of inactive node. It is not blinking.](/files/gNvyjQCXTfa0a4ogiMHO)

When we move the **Playhead** away from the layer, it gets *disabled* again and connections *stop blinking.*


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