Compare the present form and the past form
We use the present form for descriptions in the present-future.
We use the past form for descriptions in the past.
Tokyo is the capital of Japan. (true in the present)
I‘m not hungry.
Are they delicious?
Nara was the capital of Japan. (true in the past)
I wasn’t hungry after work. So I didn’t eat.
Were they delicious? There are none left.
We use the present form for fixed events in the future (these things can’t be changed). We say or know when they happen.
We use the past form for events in the past (the past can’t be changed). We say or know when they happened.
The meeting starts at 10:30.
The game isn’t on Sunday.
When does the bus leave?
The meeting started at 10:30.
The game wasn’t on Sunday.
When did the bus leave?
We use the present form for actions that happen in the present, as the speaker speaks. (These things finish in the present; they finish before we finish speaking.)
We use the past form for actions that happened in the past. (These things finished in the past.)
She doesn’t pass the ball.
Does it have the distance?
I went shopping.
He didn’t lock the door.
Did you play golf?
When we use the present form and don’t know exactly when an action happens, we understand that the speaker is speaking generally and it happens many times. (This is the most common.)