das Konzept
concept / plan
A detailed plan or basic idea for an undertaking, project, or work.
Das Architekturbüro präsentierte ein überzeugendes Konzept für das neue Museum.
The architecture firm presented a convincing concept for the new museum.

concept / plan
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concept / plan
A detailed plan or basic idea for an undertaking, project, or work.
Das Architekturbüro präsentierte ein überzeugendes Konzept für das neue Museum.
The architecture firm presented a convincing concept for the new museum.

'Konzept' (concept/plan) is often combined with certain verbs that describe the planning process. Typical phrases are: 'ein Konzept entwickeln' (to develop a concept), 'erstellen' (to create), 'ausarbeiten' (to work out), 'vorstellen' (to present), or 'umsetzen' (to implement).
Die Arbeitsgruppe muss bis nächste Woche ein Konzept erstellen.
The working group has to create a concept by next week.
To say what a plan or idea is intended for, you usually use the preposition 'für' (for) followed by the accusative.
Das ist ein interessantes Konzept für ein neues Restaurant.
That is an interesting concept for a new restaurant.
In connection with a plan, 'Konzept' (concept/plan) is often accompanied by adjectives such as 'schlüssig' (coherent), 'überzeugend' (convincing), 'durchdacht' (well thought-out), or 'innovativ' (innovative).
Sie präsentierte ein durchdachtes Konzept, das alle überzeugte.
She presented a well thought-out concept that convinced everyone.
When 'Konzept' (draft) means a text draft, it often appears with the adjective 'erstes' (first) or in a context involving writing texts, such as a speech, article, or email.
Ich habe ein erstes Konzept für den Blogartikel geschrieben.
I wrote a first draft for the blog article.
The meaning as an abstract idea is typical of technical or academic language, especially in philosophy, psychology, or linguistics. In everyday language, this use is rare.
In der Vorlesung ging es um das philosophische Konzept der Wahrheit.
The lecture was about the philosophical concept of truth.
idea
'die Idee' and 'das Konzept' can both mean the basic idea for a project or undertaking. 'Idee' is often more spontaneous and may still be very simple. 'Konzept' sounds more planned and developed. It usually describes how something is supposed to work as a whole. The words can be confused because a concept is based on an idea. If you only have a sudden thought, you are more likely to say 'Idee'. If the thought is already organized and described, 'Konzept' fits better.

Das Team schreibt ein Konzept für das neue Lernprojekt.
The team is writing a concept for the new learning project.
Am Morgen hatte Luisa eine neue Idee für die Präsentation.
In the morning, Luisa had a new idea for the presentation.