G11N is a collective term that refers to the combined I18N and L10N process.
I18N (internationalization) involves making the software flexible to handle locale specific data, e.g. handle text in local languages, handle date, time, numeric, currency data according to local formatting convention. I18N often requires redesigning parts or most of the software modules, unless they were originally written with the global market in mind. Any textual information should be isolated from the source code so that the same executable can be packaged with different language data for different markets. The textual data are extracted into resource files or database for translation or localization. A properly globalized software picks up the locale specific data and preference settings at runtime and adapt to the needs of the local markets. I18N is analogous to designing a radio with a tuner.
L10N (localization), on the other hand, mainly plugs in localized data into a I18N-ready software package. The L10N process involves translating the user interface into local language, changing graphic and icons to fit into local culture, adding data relevant to local markets (e.g. state names like New York, California are not applicable to a German market.) L10N is analogous to broadcasting different programs to different radio channel for the "radio" mentioned earlier.
I18N is about the software code. I18N is done once per software product. L10N is about the data. L10N must be repeated per language market.