What are the differences between present progressive, present continuous, and immediate present?
Those 3 terms all describe the same tense.
Those 3 terms all describe the same tense (usually called Present Continuous).
This tense is formed by
Present Simple of to be + -ing
"I am writing an answer now."
"Don't disturb her. She is learning a poem."
This tense is uaually used to indicate an action taken at the time of speaking.