Final answer:
The progressive tense in English is formed by using the present tense of the verb 'to be' and adding the present participle (-ing form) of the main verb.
Step-by-step explanation:
The verb form used to indicate the progressive tense is a combination of the present tense of the verb "to be" (am, is, are) plus the present participle of the main verb (the -ing form). For example, "is running" indicates the present progressive tense, and "was running" points to the past progressive tense. This tense is used to describe actions that are currently in progress or were in progress at a certain point in the past.