Transaction to see IDOCs for inbound and outbound delivery

Hi All

I have a very basic question. Currently I am working on the business scenario's as mentioned below.

1. Inbound delivery and outbound delivery gets created in my client's SAP system and data about this inbound and outbound delivery needs to be transmitted to 3rd Party Non SAP Warehouse via middleware through Idocs.

For the flow of IDOCs from SAP to 3rd party warehouse we will use standard SAP Idocs.

Now my very basic query is that what is the SAP transaction through which I can see standard SAP IDocs to be used for inbound and outbound delivery?

I searched SCN for Idoc for outbound delivery and came to know I can use message type DESADV and IDoc type DELVRY03. Now my query is what is the difference between message type and Idoc type and how can I search in system which message type and Idoc type to use for a scenario?

Hope I am clear in my query.

Regards

SK