Initialization of functionalities retrieves the data required to use the map functionalities and populates the functionality objects with the required information.

As of the Service Pack 1 of the 9.2 version of the Web ADF, initialization does not necessarily take place on every page postback or callback. Before accessing and using functionalities, you should ensure they are initialized.

Initialization causes the Web ADF page to contact the GIS server that provides the services used. This takes time and consumes network and server resources. Hence, you should only initialize functionalities that you will actually work with during that callback or postback. If you only need to use one (or few) functionalities, call InitializeFunctionality() for the individual item, rather than initializing all functionalities with InitializeFunctionalities.

Reference