The Progressive is used with situations we are in the middle of now:
Or situations we will be in the middle of at a future moment:
Or situations we were in the middle of at a past moment:
A situation in progress might be incomplete:
We can use the Simple Tenses with serial or permanent situations. The Progressive shows that the situation is temporary:
It can also show that the situation has changed recently:
We use the Progressive with situations where something is progressively increasing or decreasing:
Even if the situation continues for a long time:The universe is expanding.
With words like forever, always or constantly, the Progressive tells us that the situation happens more often than normal:
We often use it in this way to express irritation:Why are you forever criticizing her?