When slot="error" is displayed

I found in the ion-item documentation, that ion-note slot=“error” is placed under the item and displayed when an error is detected.

Can you please specify these errors?

Example:

<IonItem>
          <IonLabel>Helper and Error Text</IonLabel>
          <IonInput></IonInput>
          <IonNote slot="helper">Helper Text</IonNote>
          <IonNote slot="error">Error Text</IonNote>
</IonItem>