GraphQL is quite different from normal REST endpoints and it can take some time to grasp the concept. Instead of having multiple endpoint you only have one.
It's recommended to read Introduction to GraphQL and Queries and Mutations over at Learn about GraphQL before start using our implementation.

Using the GraphQL endpoint, you can do two types of operations. Querying and mutating.

Querys are used to get one specific object or to search for a list of objects that match a given search query.
Mutations are used to perform certain actions and alter objects.

The examples below are quite simple, regarding the request body. In production you'll probably want to give the queries and mutations a operation name and also looking into the use of variables.

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Pro Tip
Use GraphiQL to get intellisense and full documentation. If you are using Chome, try the ChromeiQL extension.
When using ChromeiQL, or any other GraphiQL client, you need to add an API key to the request. The easiest way is to add a query parameter apikey=<your API key> to the request.

Available entities

The following entities can be fetched and edited.
Organizations
Persons
Deals