DOC: Improve DataFrameGroupBy.std ddof doc (#59425)

improve ddof doc of DataFrameGroupBy.std

Author: KevsterAmp

pandas/core/groupby/groupby.py

@@ -2437,7 +2437,8 @@ def std(
         Parameters
         ----------
         ddof : int, default 1
-            Degrees of freedom.
+            Delta Degrees of Freedom. The divisor used in calculations is ``N - ddof``,
+            where ``N`` represents the number of elements.
 
         engine : str, default None
             * ``'cython'`` : Runs the operation through C-extensions from cython.