Difference between UserInfo.getUiTheme() and UserInfo.getUiThemeDisplayed() in Salesforce

Salesforce currently supports the below themes
Theme1—Obsolete Salesforce theme
Theme2—Salesforce Classic 2005 user interface theme
Theme3—Salesforce Classic 2010 user interface theme
Theme4d—Modern “Lightning Experience” Salesforce theme
Theme4t—Salesforce mobile app theme
Theme4u—Lightning Console theme
PortalDefault—Salesforce Customer Portal theme
Webstore—Salesforce AppExchange theme

UserInfo.getUiTheme()
This method returns the preferred theme for the current user.

UserInfo.getUiThemeDisplayed()

Use getUiThemeDisplayed to determine the theme actually displayed to the current user.