A structure is created by defining deal configuration data in a structure template (see What Is a Structure Template?). Once this data is defined, the structure template can then be saved as a structure.
A structure can be saved in either the My Portfolios or the Public Portfolios folder. If you save it in the Public Portfolios folder, other users can access it and use it.
Unlike a structure template, a structure can contain deal configuration data, including market data and strike and notional values. The difference between a structure and a template is that a structure can contain explicit data, not just relative data. That is, it can contain actual dates, not just tenors.
In the Portfolio Management window a structure is indicated by an [S].