The present continuous tense expresses an activity that is in progress at the moment of speaking. It is formed using the present form of the verb "to be" along with the verb ending in "-ing". Examples of time signals that can be used with the present continuous include now, right now, this morning/night/afternoon. For example, "She is talking on the phone right now" or "Mike is not going to school right now because it's summer." The tense is used to describe temporary activities or situations.