# Concept Invantive Control for Excel includes the following concepts: -  Model; -  Block; -  Parameter; -  Extension; -  Pending change; -  Synchronise. The image shows an overview of the concepts and the relationships between them.  Model A model is a representation of a formula in the Invantive Control for Excel format. The formula uses input parameters in the form of data from a database. These input parameters are then processed using Excel expressions and the result is displayed. The input parameters can be modified, added or removed. However, these changes do affect the database. For example, the model contains the definition of all organisations from a business object. See [Model Editor](invantive-control-model-editor) for more information. Block A block is an adjacent area in an Excel worksheet. A block contains data from a database retrieved by a query during the last synchronisation and contains the data that still needs to be written during the next synchronisation. A block spans one of the dimensions: cell, column, row or worksheet. See [Blocks](invantive-control-blocks) for an example.  Parameter A parameter is a filter that can be set to retrieve a subset of a block’s data from the fact database. By specifying a parameter, you ensure that only data matching the filter settings is retrieved from the database. See [Parameter values](invantive-control-parameter-values) for setting parameters. Extension An extension is a script integrated into the model’s execution process. An extension enriches a Model with functionality not included as standard in Invantive Control for Excel. An example of an extension is using a button to automatically add data to the worksheet. See [Extensions](invantive-control-extensions) for more information. Pending change These are changes to the model user’s local data that are ready to be sent to the fact database. The fact database serves as the central repository for facts outside an Excel worksheet. A pending change could, for example, be an adjustment to a cell value in Excel, and this change has yet to be sent to the fact database. See [Pending Changes](invantive-control-openstaande-wijzigingen) for more information. Synchronise You use Synchronise to send pending changes to the fact database and to retrieve the latest data from the fact database. The Upload option sends the changes that have not yet been sent to the fact database. The Download option retrieves the latest data from the fact database and processes it in the data block. See [Model User Interface](invantive-control-user-interface-model-user) for more information.