die Vorstellung
idea
An image, idea, or thought that one forms in one's mind about something or someone.
Ich habe eine klare Vorstellung davon, wie mein Haus aussehen soll.
I have a clear idea of what my house should look like.

idea / performance / introduction
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idea
An image, idea, or thought that one forms in one's mind about something or someone.
Ich habe eine klare Vorstellung davon, wie mein Haus aussehen soll.
I have a clear idea of what my house should look like.

'Die Vorstellung' is the noun form of the separable verb 'vorstellen' (to imagine/introduce/present). The basic idea is to 'place' something 'in front of' someone or oneself: an idea before the mind's eye, a person before a group, or a piece before an audience.
Kannst du dir das vorstellen?
Can you imagine that?
In the meaning of 'Idee' (idea), the fixed expression 'eine Vorstellung von etwas (Dativ) haben' (to have an idea of something) is often used. It expresses whether one has a clear image or concept of something.
Ich habe noch keine genaue Vorstellung von meinem zukünftigen Beruf.
I don't yet have a precise idea of my future profession.
You can recognize the meaning 'Aufführung' (performance) from the context: words like 'Theater' (theater), 'Kino' (cinema), 'Karten' (tickets), 'Beginn' (start), 'Pause' (intermission), or 'ausverkauft' (sold out) clearly point to this meaning.
Gehen wir heute Abend in die Spätvorstellung?
Shall we go to the late showing tonight?
The meaning 'sich vorstellen' (to introduce oneself) is central in a professional context. The noun 'die Vorstellung' (introduction) is at the core of the important word 'das Vorstellungsgespräch' (job interview).
Die erste Runde der Vorstellungen ist abgeschlossen.
The first round of introductions is complete.
In the meaning of 'Meinung' (opinion) or 'Wert' (value), the word is very often used in the plural. One then speaks of a person's 'Vorstellungen' (notions/ideas), often in combination with adjectives such as 'moralisch' (moral), 'politisch' (political), or 'konservativ' (conservative).
Seine moralischen Vorstellungen sind sehr streng.
His moral beliefs are very strict.
picture / image
'das Bild' and 'die Vorstellung' can both mean something you have in your mind. 'die Vorstellung' is often an idea, a thought, or an expectation. 'das Bild' sounds more visual: you almost see a scene internally or have a particular impression. Learners may confuse the words because in both cases, you are not talking about a real photo. 'Vorstellung' fits especially when talking about plans, expectations, or ideas. 'Bild' fits well when you want to describe an inner impression.

Meine Vorstellung von dem Kurs war ganz anders.
My idea of the course was completely different.
Von der neuen Wohnung habe ich schon ein genaues Bild im Kopf.
I already have a clear picture of the new apartment in my head.