SENTENCE: The elephant is eating hay. 'is eating' is a present progressive according to my textbook. In my textbook, it says that a present progressive verb is made up of the present tense of the helping verb 'be' and the present participle of the main verb. What does this mean?

Present form of verb 'be' is 'is' or 'am' or 'are' and present participle of the main verb means -ing form of verb indicating continuous action.

Explanation:

present form

obama was told in early july 2004 that he was chosen to deliver the address, and he largely wrote the speech himself, with later edits from the kerry presidential campaign.