The present continuous tense is used to describe actions or events that are happening right now, at the moment of speaking, or to talk about future plans or arrangements.

Structure
The structure of the present continuous tense is:

Subject + am/is/are + verb(-ing)

- "Am" is used with the subject I.
- "Is" is used with singular subjects (he, she, it).
- "Are" is used with plural subjects (you, we, they).

Usage of present continuous tense - 

1. To describe actions happening at the moment of speaking
   - Example: She is reading a book.
     - (This means she is reading right now.)

2. To describe temporary actions or situations
   - Example: He is staying with his parents for the summer.
     - (This is a temporary situation.)

3. To describe actions that are in progress but not necessarily happening at the exact moment of speaking
   - Example: They are building a new library.
     - (This action is ongoing, though it may not be happening right now.)

4. To talk about future plans or arrangements
   - Example: We are meeting them tomorrow.
     - (This is a planned event in the future.)

Examples of present continuous tense
- I am working on a new project.
- They are playing soccer in the park.
- She is learning Spanish.
- We are leaving for vacation next week.

Time Expressions Often Used
Common time expressions with the present continuous tense include:
- now, right now, at the moment
- currently, at present
- today, this week, this month (for temporary actions)
- tomorrow, next week, on [specific day] (for future plans)

Key Points of present continuous tense
- Focuses on actions happening right now or around the present time.
- Can also be used to describe future plans or arrangements.
- Requires am/is/are followed by a verb in the -ing form (present participle).

The present continuous tense is ideal for talking about actions in progress, temporary situations, or definite future plans.