spielen
to play
To occupy oneself for fun with a game, toy, or activity, often used for children.
Die Kinder spielen draußen im Sandkasten.
The children are playing outside in the sandbox.

to play
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to play
To occupy oneself for fun with a game, toy, or activity, often used for children.
Die Kinder spielen draußen im Sandkasten.
The children are playing outside in the sandbox.

The exact meaning of 'spielen' depends strongly on the object or preposition. A musical instrument or a sport is used directly in the accusative. A setting takes 'in'. An idea that one is considering is used with 'mit dem Gedanken' (with the thought).
Sie spielt Geige.
She plays violin.
When children (or adults too) occupy themselves with a toy or another person, the preposition 'mit + dative' is used.
Der Junge spielt mit seinem neuen Auto.
The boy is playing with his new car.
With most ball sports and board games, 'spielen' is used directly with the accusative object. You don't need a preposition.
Spielst du gerne Basketball?
Do you like playing basketball?
When talking about musical instruments, 'spielen' is connected directly with the instrument in the accusative. You don't need a preposition as in English.
Er lernt seit einem Jahr, Gitarre zu spielen.
He has been learning to play guitar for a year.
When an actor portrays a character, that character is the direct accusative object of 'spielen'. Typical objects are: 'die Hauptrolle' (the leading role), 'eine Nebenrolle' (a supporting role), 'den Helden' (the hero), or 'den Bösewicht' (the villain).
In seinem nächsten Film spielt er einen Detektiv.
In his next film, he plays a detective.
The idiom 'eine Rolle spielen' means 'to be important' or 'to be relevant'. The negation 'keine Rolle spielen' is also very common and means 'to be unimportant'.
Das Alter spielt für diese Position keine Rolle.
Age doesn't play a role for this position.
To describe the place or time of the plot of a film, book, or play, you use the structure 'spielen in + dative'.
Der Roman spielt im Paris des 19. Jahrhunderts.
The novel is set in 19th-century Paris.
In the context of gambling, you use 'spielen um + accusative' to name the stake or prize. You can also use 'auf + accusative' to say what someone is betting on.
Sie spielen jeden Freitag Poker um Geld.
They play poker for money every Friday.
The expression 'mit dem Gedanken spielen, etwas zu tun' (to toy with the idea of doing something) means that one is considering an idea or plan but is still undecided. The preposition 'mit' and the infinitive construction with 'zu' are fixed components.
Sie spielt mit dem Gedanken, nach Australien auszuwandern.
She is toying with the idea of emigrating to Australia.
The phrase 'verrückt spielen' (to act up) is colloquial. It is used for devices, technical systems, or even body parts that are not functioning properly or are behaving unpredictably.
Mein Computer spielt in letzter Zeit ständig verrückt.
My computer has been constantly acting up lately.
to run
'spielen' and 'laufen' can both occur with films, series, or plays, but they do not mean the same thing. 'spielen' says where or when the action of a film or book is set. 'laufen' says that a film or program is currently being shown or broadcast. Learners may confuse the words because you hear both in media contexts. Remember: a film 'spielt in Berlin' (is set in Berlin), but it 'läuft im Kino' or 'läuft im Fernsehen' (is showing at the cinema or is on television).

Der neue Krimi spielt in einer kleinen Stadt an der Küste.
The new crime novel is set in a small town on the coast.
Im Kino läuft heute Abend ein Film über eine lange Reise.
A film about a long journey is showing at the cinema this evening.