An interrogative sentence asks a question. It ends with a question mark.
Did you read the article about migrating geese patterns?
How do spell your last name?
Mr. Young owns a kennel?
A declarative question is a question with the grammar of a statement but said with intonation that shows it is a question.
An indirect question is used when someone wants to ask something in a more polite way, e.g. 'I was wondering if you could help me.' (indirect question) instead of 'Could you help me?' (direct question).
Question tag, tag question
A phrase that is added to the end of a sentence to make it a question, or to check that someone agrees with the statement just made, e.g. it's very cold, isn't it? It isn't very far, is it?