The Lightning Component presents the user interface along with the functional units used within the Lightning Component framework and, in the context of the framework for our "Search First Before You Create" Lightning Component, is described by Salesforce as follows:
"Components are the functional units of the Lightning Component framework.
A component encapsulates a modular and potentially reusable section of UI, and can range in granularity from a single line of text to an entire application."
A component encapsulates a modular and potentially reusable section of UI, and can range in granularity from a single line of text to an entire application."
Reference:
Lightning Components Developer Guide: Creating Components
https://developer.salesforce.com/docs/atlas.en-us.lightning.meta/lightning/components_overview.htm
Lightning Components Developer Guide: Creating Components
https://developer.salesforce.com/docs/atlas.en-us.lightning.meta/lightning/components_overview.htm