Quiero que me ayudes.
English: I want you to help me.
Noun subordinate clauses ('oraciones subordinadas sustantivas') in Spanish are clauses that work like a noun in a sentence. They can be the subject, object, or complement of the main verb.
Use noun subordinate clauses in Spanish when you want to express wishes, needs, opinions, doubts, or information. They often answer 'what?' or 'who?' after the verb.
Quiero que me ayudes.
English: I want you to help me.
No sé si ella viene.
English: I don't know if she is coming.
Me alegra que estés aquí.
English: I'm happy that you are here.
Es importante estudiar.
English: It is important to study.