https://goteleport.com/docs/admin-guide/#labeling-nodes-and-applications

In addition to specifying a custom nodename, Teleport also allows for the application of arbitrary key-value pairs to each node or app, called labels. There are two kinds of labels:

• static labels do not change over time, while teleport the process is running. Examples of static labels are the physical location of nodes, the name of the environment (staging vs production), etc.
• dynamic labels also known as "label commands" allow to generate labels at runtime. Teleport will execute an external command on a node at a configurable frequency and the output of the command becomes the label value. Examples include reporting load averages, presence of a process, time after the last reboot, etc.