L3: The use of curly braces in prompt template

Can anyone explain the use of 4 layers, 2 layers and one single layer of curly braces in the following prompt template?

MULTI_PROMPT_ROUTER_TEMPLATE = “”"Given a raw text input to a
language model select the model prompt best suited for the input.
You will be given the names of the available prompts and a
description of what the prompt is best suited for.
You may also revise the original input if you think that revising
it will ultimately lead to a better response from the language model.

Return a markdown code snippet with a JSON object formatted to look like:

    "destination": string \ name of the prompt to use or "DEFAULT"
    "next_inputs": string \ a potentially modified version of the original input

REMEMBER: “destination” MUST be one of the candidate prompt
names specified below OR it can be “DEFAULT” if the input is not
well suited for any of the candidate prompts.
REMEMBER: “next_inputs” can just be the original input
if you don’t think any modifications are needed.


<< INPUT >>

<< OUTPUT (remember to include the ```json)>>“”"