What are Local and Global ids with respect to Salesforce Lightning Component?

Component IDs
A component has two types of IDs: a local ID and a global ID. You can retrieve a component using its local ID in your JavaScript code. A global ID can be useful to differentiate between multiple instances of a component or for debugging purposes.

Local IDs
A local ID is an ID that is only scoped to the component. A local ID is often unique but it’s not required to be unique.
Create a local ID by using the aura:id attribute. For example:
Find the button component by calling cmp.find(“button1”) in your client-side controller, where cmp is a reference to the component containing the button.

Global IDs
Every component has a unique globalId, which is the generated runtime-unique ID of the component instance. A global ID (1) is not guaranteed to be the same beyond the lifetime of a component, so it should never be relied on. A global ID can be useful to differentiate between multiple instances of a component or for debugging purposes.

Hello,

A component has two types of IDs: a local ID and a global ID.
You can retrieve a component using its local ID in your JavaScript code.
A global ID can be useful to differentiate between multiple instances of a component or for debugging purposes.
Local ID is created by using the aura:id attribute.
example
To find the local ID for a component in JavaScript, use cmp.getLocalId()
Every component has a unique globalId, which is the generated runtime-unique ID of the component instance.
A global ID is not guaranteed to be the same beyond the lifetime of a component, so it should never be relied on

Thanks