[SPARK-49606][PS][DOCS] Improve documentation of Pandas on Spark plot…

…ting API

### What changes were proposed in this pull request?
Improve documentation of Pandas on Spark plotting API following pandas 2.2 (stable), see https://pandas.pydata.org/docs/reference/frame.html.

### Why are the changes needed?
Better documentation and parity with pandas.

### Does this PR introduce _any_ user-facing change?
Doc changes only.

### How was this patch tested?
Existing tests.

### Was this patch authored or co-authored using generative AI tooling?
No.

Closes apache#48083 from xinrong-meng/doc_impr.

Authored-by: Xinrong Meng <xinrong@apache.org>
Signed-off-by: Dongjoon Hyun <dongjoon@apache.org>

python/pyspark/pandas/plot/core.py

@@ -540,7 +540,7 @@ def line(self, x=None, y=None, **kwargs):
         """
         Plot DataFrame/Series as lines.
 
-        This function is useful to plot lines using Series's values
+        This function is useful to plot lines using DataFrame’s values
         as coordinates.
 
         Parameters
@@ -606,6 +606,12 @@ def bar(self, x=None, y=None, **kwds):
         """
         Vertical bar plot.
 
+        A bar plot is a plot that presents categorical data with rectangular
+        bars with lengths proportional to the values that they represent. A
+        bar plot shows comparisons among discrete categories. One axis of the
+        plot shows the specific categories being compared, and the other axis
+        represents a measured value.
+
         Parameters
         ----------
         x : label or position, optional
@@ -797,7 +803,17 @@ def barh(self, x=None, y=None, **kwargs):
 
     def box(self, **kwds):
         """
-        Make a box plot of the Series columns.
+        Make a box plot of the DataFrame columns.
+
+        A box plot is a method for graphically depicting groups of numerical data through
+        their quartiles. The box extends from the Q1 to Q3 quartile values of the data,
+        with a line at the median (Q2). The whiskers extend from the edges of box to show
+        the range of the data. The position of the whiskers is set by default to
+        1.5*IQR (IQR = Q3 - Q1) from the edges of the box. Outlier points are those past
+        the end of the whiskers.
+
+        A consideration when using this chart is that the box and the whiskers can overlap,
+        which is very common when plotting small sets of data.
 
         Parameters
         ----------
@@ -851,9 +867,11 @@ def box(self, **kwds):
     def hist(self, bins=10, **kwds):
         """
         Draw one histogram of the DataFrame’s columns.
+
         A `histogram`_ is a representation of the distribution of data.
         This function calls :meth:`plotting.backend.plot`,
         on each series in the DataFrame, resulting in one histogram per column.
+        This is useful when the DataFrame’s Series are in a similar scale.
 
         .. _histogram: https://en.wikipedia.org/wiki/Histogram
 
@@ -902,6 +920,10 @@ def kde(self, bw_method=None, ind=None, **kwargs):
         """
         Generate Kernel Density Estimate plot using Gaussian kernels.
 
+        In statistics, kernel density estimation (KDE) is a non-parametric way to
+        estimate the probability density function (PDF) of a random variable. This
+        function uses Gaussian kernels and includes automatic bandwidth determination.
+
         Parameters
         ----------
         bw_method : scalar