Explain the usage of the present continuous tense.

The present continuous tense is used to describe actions or situations that are happening at the present moment or around the time of speaking. It is formed by using the present tense of the verb "to be" (am, is, are) followed by the present participle form of the main verb (-ing form).

There are several situations in which the present continuous tense is commonly used:

1. Actions happening now: We use the present continuous tense to talk about actions that are taking place at the moment of speaking. For example: "I am studying for my exam right now."

2. Temporary situations: The present continuous tense can be used to describe temporary situations or actions that are happening around the present time. For example: "She is working as a waitress while she looks for a permanent job."

3. Future arrangements: We can also use the present continuous tense to talk about future arrangements or plans that have already been made. For example: "I am meeting my friends for dinner tomorrow."

4. Annoyance or irritation: The present continuous tense can be used to express annoyance or irritation about a repeated action. For example: "He is always interrupting me when I'm speaking."

5. Changing or developing situations: The present continuous tense can be used to describe situations that are changing or developing over time. For example: "The weather is getting colder as winter approaches."

It is important to note that the present continuous tense is not used for permanent or general situations. For those cases, we use the present simple tense.