What is an interrogative sentence?  An interrogative asks a question, and ends with a question mark.
Are you going to study today?
An interrogative sentence re-orders a declarative sentence.
You are going to study today.

A famous interrogative sentence:
“Wherefore art thou Romeo?” Juliet, Romeo & Juliet. Shakespeare

In an interrogative sentence, the verb in the verb phrase appears before the subject. This is directly opposite to the structure in a declarative sentence, exclamatory or imperative sentence. In these, the subject appears before the verb.
Interrogative sentences are common because the question and answer form of dialogue is a necessary part of everyday speech and conversation.

examples of interrogative sentence types.

Yes/No interrogative sentence. These sentences are formed as questions which require a yes or no answer
“Do you like cats?”

Alternative interrogative sentence. These are sentences formed to give you an answer from 2 or more options.
“Would you like potatoes or rice with your steak?”

Wh-interrogative sentence. These are aimed to be open ended questions, the sentence begins with  The answer required is more than a no or yes, and the interrogative sentence does not contain an either – or choice of answers.
Wh-interrogatives sentences begin with a wh-word and call for an open-ended answer. A yes or no answer isn’t appropriate for these questions, nor does the question  provide alternative answers.  The answer can be a simple response or complex explanation. By the wh- words, we mean who, which, what, etc?  These are called interrogative pronouns. We use interrogative pronouns to ask a question.
“What is you name?”
“Where are we going?”
“Which exit do I take?”

Tag interrogative sentence is when questions  are attached to a declarative statement, thereby making the sentence an interrogative one.
“You know how to cook these, don’t you?”

Interrogative sentences can also be in terms of structure a declarative sentence, except that it has a question mark at the end. You intone the end of the sentence by lifting it a bit to indicate that this is a question;
You’re flying to Mexico?

An interrogative sentence is very simple to identify.  They always ask a question or request information.  Simply look for the question mark at the end and you’ll have no problem finding or understanding the function of interrogative sentences. You use an interrogative sentence to obtain information.