added README

Author: devAbnull

README.md

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+# Understanding GraphQL
+
+**GraphQL** ( Graph Query Language ) is a query language for APIs and a server-side runtime for executing queries by using a type system you define for your data.
+
+In REST APIs, there's clearly a defined structure of information returned from each endpoint (like to fetch posts endpoint would be like _http://some.api.com/posts_). GraphQL always exposes only one endpoint, allowing the client to decide what data it really needs from a predefined pattern.
+
+## Query
+
+Queries are used to make requests for data from the server. As seen in below example, the query has exactly the same shape as the result.
+
+Example for query:
+
+```
+{
+  me {
+    name
+  }
+}
+
+```
+
+returns a JSON:
+
+```
+{
+  "me": {
+    "name": "Morty"
+  }
+}
+```
+
+## Mutations
+
+In GraphQL, Mutations are used to modify data on server. **mutation** is just a keyword.
+Technically any query could be implemented to update data. However, it's an established convention that any operations that causes writes should be sent explicitly via a mutation.
+
+Mutations are really much like the query objects, they too have a type, arguments and a resolve function.
+
+Just like in queries, if the mutation field returns an object type, nested fields can also be fetched.
+
+example for mutation:
+
+```
+mutation {
+  addUser(firstName: "AB", age:23, companyId:"2") {
+    id
+    firstName
+    company {
+      name
+    }
+  }
+}
+```
+
+_for more details_ checkout official docs at https://graphql.org/learn/