Where I can read more about ID type? There is any coercion? It's string or number in clojure?

Both I think, I used a number and it worked. Here it's a string, https://github.com/walmartlabs/lacinia/blob/master/dev-resources/basic-vars.edn

ID has some special meaning?

I’m also really new to this, but as I understand it’s interperted as some identifier without meaning. To js ir will always be a string. So when for example your id’s are generated sequentially you might also add the same property as a sequence_number as an int. Also I assume it’s non null by default.

ID: The ID scalar type represents a unique identifier, often used to refetch an object or as the key for a cache. The ID type is serialized in the same way as a String; however, defining it as an ID signifies that it is not intended to be human‐readable. http://graphql.org/learn/schema/