What is the difference between
I drank a tea
I had a tea
I was drinking a tea
I am driving a car after work
I was driving a car after work
I drove a car after work
I had drove a car after work

Question

What is the difference between
I drank a tea 
I had a tea
I was drinking a tea
I am driving a car after work
I was driving a car after work
I drove a car after work
I had drove a car after work

Answer

You are asking us to explain the difference between the usage of 4 tenses.  This is a huge question.

Answer

The tea sentences mean the same but we don't use "a" (for some reason)
For driving a car after work the 3rd sentence is grammatically correct.