Is there any API available to fetch workitems type?

for a workitem , it will have a display name, which gets displayed in the UI and an identifier value like com.ibm.___ which will be used at the backened. How can we fetch it?

That is incorrect. As far as I am aware a work item das a unique ID/identifier like 345.

com.ibm.___ is part of a name pattern that does not reveal any relevant information. 

Since the question does not seem to be asked in an answerable way: You can find the available APIs here: https://jazz.net/wiki/bin/view/Deployment/CLMProductAPILanding

As far as I am aware a work item das a unique ID/identifier like 345.

com.ibm.___ is part of a name pattern that does not reveal any relevant information in the context of the question. 

Since the question does not seem to be asked in an answerable way: You can find the available APIs here: https://jazz.net/wiki/bin/view/Deployment/CLMProductAPILanding 

Any work item has an ID - an integer as already stated. It is usually necessary to know the ID to access the work item in any API. If you have access to a work item the ID is always accessible.

A work item usually has a summary which is accessible in any supported API, if you have the work item.

A work item always has a type. This is accessible in any API I am aware of. 

 Ok Thanks for the info, identifier means the id of the workitem, But yes I want to fetch the type of all workitems in project area

Use OSLC query.