Present Simple: I write an essay every day.
Present Continuous: I am writing an essay right now.
Present Perfect: I have written an essay this week.
Simple Past: I wrote an essay yesterday.
Past Continuous: I was writing an essay at this time yesterday.
Past Perfect: I had written an essay before the deadline.
Future Simple: I will write an essay tomorrow.
Future Continuous: I will be writing an essay at this time tomorrow.