The standard tuning for a violin, is GDAE, where G is the lowest string and E is the highest. However, alternate tunings are often used for fiddle playing.
How to tune a fiddle?
Often fiddlers use alternate tunings for fiddling especially for old time country fiddling.
Cross tuning is the most common alternate tuning - the most common cross tunning is AEAE, where A is the lowest string and E is the highest.
Another very common cross tunning for fiddling is GDGD, where G is the lowest string and D is the highest.
Another alternate tunings us for fiddling is DDAD called dead man's tuning - this tuning is often used for fiddling Hoedown.
I have a web page with more information about cross tunning and other alternate tunings.
For more information about fiddling using cross tunning and other tunings, visit my How to Fiddle web page
How to fiddle YouTube playlist - mostly cross tuned fiddle AEAE https://www.youtube.com/watch?v=PktuW2dtFjI&list=PLrSYSyY0UgdJFYokiWOyWbcSjW5cacaDB
Many folks don't realize that many fiddle tunes on the violin are often played with different tunings like cross tunning GDGD or AEAE. You can also cross tune a viola. Cross tunning gives the fiddle sound to the violin or viola and is generally easier for a beginner to learn. Also cross tunning makes it easy to play chords / double stops in the key you are cross tuned to. Cross tunning is especially used in old time music and is especially good for solo fiddle playing because of the ease of chording and producing drone tones along with the melody.