The standard 4 string Ukulele is tuned with G C E and A notes. (Thickest to thinnest string or low to high string)
The baritone ukulele is sometimes tuned like that of bottom 4 stings of the Standard Guitar tuning - E B G D (Thinnest to thickest sting) and advanced players use A D F# B in Tenor and Baritone Ukulele.
Get Start With Ukulele