Defining GROUP (or Custom Groups in EndNote X2) is good in order to organize our references. We could find references easily based on the groups, e.g. references relating with ‘SMS’, specifically with ‘e-government’, etc.
Basically, all of our references will be stored in the same place (EndNote Library). When we define a Group (e.g. ‘SMS’) and drag a reference into the ‘SMS’ group, this action actually is just copying the reference data from ‘All Reference’ into ‘SMS’ group. When we delete the reference in the group, it will not delete the reference in ‘All Reference’, but when we delete the reference in ‘All Reference’ it will delete the reference in the group.
To make a group: simply just right click on the column ‘Groups’ and choose ‘Create Group’
To cathegorize/add references into group: just drag the reference into group.