Explain the concept of past continuous tense.

The past continuous tense is used to describe an ongoing action or event that was happening in the past. It is formed by using the past tense of the verb "to be" (was/were) followed by the present participle form of the main verb (-ing form).

This tense is used to emphasize the duration or progress of an action in the past. It is often used to set the background or context for another action that happened in the past.

For example:
- "I was studying when the phone rang." (The action of studying was in progress when the phone rang.)
- "They were playing soccer when it started raining." (The action of playing soccer was happening when it started raining.)

The past continuous tense can also be used to describe two ongoing actions happening simultaneously in the past. In this case, two past continuous verbs are used in the same sentence.

For example:
- "She was cooking dinner while he was watching TV." (Both actions of cooking dinner and watching TV were happening at the same time in the past.)

Overall, the past continuous tense helps to provide a more detailed and vivid description of past events by highlighting the ongoing nature of actions in the past.