The .groupBy(...) transformation performs data aggregation based on the value (or values) from a column (or multiple columns). In SQL syntax, this equates to GROUP BY.

Look at the following code:

(
    sample_data_schema
    .groupBy('RAM')
    .count()
    .show()
)

It produces this result:

In SQL syntax, this would be:

SELECT RAM
    , COUNT(*) AS count
FROM sample_data_schema
GROUP BY RAM