Wording and clarity edits

[cassws]

Phrasing changes to increase clarity in some parts of lesson, such as:

• Rewording "methods" as "processes" so learners don't confuse with object methods
• Ambiguity re: CSV's and separators
• Acknowledge dimension block at end of console output for dataframe (without .head() or print(df)
• misc. phrasing

Note that the clarity around methods would be compatible with the edits in #452 (which I think are great!)

Thank you for considering!