Idea vs. noción
While both idea and noción can translate to idea or having a clue about something, they are used in slightly different contexts. The word idea is the most common, everyday term for a thought, a plan, or general knowledge. On the other hand, noción is slightly more formal and often refers to a basic understanding, a foundational concept, or a vague awareness of something, such as keeping track of time.
Idea
The word idea is the most versatile and frequently used term to express a mental concept, a thought, an intention, or having a general clue about a situation.
No tengo idea de cómo llegar a la estación de tren.
(I have no clue how to get to the train station.)
¿Tienes alguna idea de lo que está pasando en la oficina?
(Do you have any idea what is happening in the office?)
El profesor nos dio una idea muy clara de los temas del examen.
(The teacher gave us a very clear idea of the exam topics.)
Se me ocurrió una idea brillante para resolver el problema.
(A brilliant idea occurred to me to solve the problem.)
Ellos no tienen ni idea del costo de vida en esta ciudad.
(They have absolutely no clue about the cost of living in this city.)
Noción
The word noción is a more formal term used to describe a fundamental concept, a rudimentary or basic understanding of a subject, or a vague awareness.
El niño pequeño todavía no tiene noción del peligro.
(The small child does not yet have a concept of danger.)
Tengo una vaga noción de cómo funciona el motor de este coche.
(I have a vague notion of how the engine of this car works.)
Perdí por completo la noción del tiempo mientras jugaba videojuegos.
(I completely lost track of time while playing video games.)
El curso introductorio ofrece unas nociones básicas de programación.
(The introductory course offers some basic knowledge of programming.)
No tenía ni la menor noción de que el evento había sido cancelado.
(I did not have the slightest clue that the event had been canceled.)
Summary
In short, use idea for everyday thoughts, plans, and expressing whether you have a clue about something. Use noción when you want to express a more formal, basic understanding, foundational concepts, or a vague awareness of abstract things like danger or time.