Functions in pyspark.sql.functions build column expressions. Import them as F so F.col('amount') is visibly different from a Python string. A string by itself is a Python value; F.lit turns a constant into a column expression. withColumn returns a new DataFrame with the named expression added or replaced.
Aster Supply's status and region fields need consistent text for reporting. Use trim to remove surrounding spaces and upper or lower to normalize case when the business rule permits it. A when expression chooses values row by row. Finish it with otherwise when unmatched rows need an explicit label; without it, those rows become NULL. These are transformations, so display the final DataFrame to inspect their effect. Renaming a column changes its name rather than its values.