Sensors - an entity or a sensor in YAML configuration?

I’ve been adding sensors on a Zigbee network using deCONZ. HA classes them as Entities when I look in the Code Editor on the UI Card. There is nothing in the Configuration YAML file.
Many user videos, however, show people creating a Sensor file in the YAML configuration. and then adding all the sensor details. Why is there a different approach?

Are you saying these videos are showing how to manually configure Zigbee-based sensors in configuration.yaml? Post a link to one or two.

Or are they showing how to configure sensors based on other integrations such as Template, MQTT, RESTful, etc?

Thank you for the reply, 123 Taras. These are fair questions. I’ve noticed there is no sensor file in the configuration.yaml. As a first step, should I add the following line to the configuration.yaml file?

sensor: !include sensor.yaml

As a second step, I should the create a file in the File Editor called sensor.yaml

It’s my first time.