Sentences can be active (statements), interrogative (questions) or imperative (orders).
The cat is drinking its milk. (active)
Is the cat drinking its milk? (interrogative)
Drink your milk! (imperative)
To convert one type of sentence into another, we need to make changes to the verb and alter the word order.
To make a statement into a question the verb is usually moved to the beginning of the sentence. If the verb is made up of more than one word, only the first part of the verb is moved to the beginning of the sentence.
Is the cat drinking its milk?
An imperative sentence usually starts with the verb.
Drink your milk!
As the cat is being spoken to, we do not need to include the words 'the cat'. Imperative sentences often end with an exclamation mark, but not always.