What are adapters used for in IBM Security Identity Manager?

When do we use these adapters? How are they used by services and TDI? Please answer in Layman language if you can.

Adapters (Earlier also know as ITIM agents) are used as a connection medium between the ITIM and the endpoint. Whenever we request some operation in ITIM, for example an add account, the corresponding changes need to be done on the endpoint too so that ITIM and endpoint remain in sync. These changes are automatically done by ITIM and if the operation is successful the results are updated at ITIM side (ITIM's LDAP) or else they are reverted back to old stage. A service we create in ITIM is part of the adapter package and represents the endpoint on ITIM side. The adapter jar file (that we import in ITIM under service types) has some files which describe the endpoint, like the service form parameters, the account form parameters, the object class of account,service groups etc (Because each endpoint will have different attributes and hence schema for account etc). These parameters are then entered by the user and on an operation are passed forward to the adapter. The adapter reads this and performs operation on the endpoint.

As you can see in the following image:-

The adapter is basically the communication medium between ITIM and endpoint. The adapters are also of two types DAML based and Agentless/TDI based adapters. You can read more about them on IBM knowledge center. Usually a adapter is Java/C++ or some other language code that uses some API (to connect to the endpoint and perform operation) and performs user management operations on the endpoint for ITIM (as the ITIM operation requested like add user/delete user etc).

Hope that gives you a slight glimpse of ITIM adapters :)