Just like other Python libraries, the API has Python modules, classes, functions, and types that can be used for managing and working with elements of the ArcGIS platform information model. Because the API is meant for different user groups that require their own unique tools, the API has been organized into 13 different modules. It's not necessary to cover them all here, but the most important ones for this chapter are mentioned as follows:

1. The GIS module: This is the most important module and is the entry point to a GIS that is hosted in ArcGIS Online or ArcGIS Portal. The GIS module lets you manage users, groups, and content in a GIS. The term GIS refers in this context to a collaborative environment for creating, visualizing, and sharing maps, scenes, apps, layers, analytics, and data.
2. The features module: This module represents the vector data part of the API. Vector data is represented through this module as feature data, feature layers, or collections of feature layers. Individual data elements are represented by feature objects, while classes such as FeatureSet, FeatureLayer, and FeatureCollection represent different groupings of feature data.
3. The raster module: This module contains classes and raster analysis functions for working with raster data and imagery layers. Whereas the features module represents the vector data component of the API, the raster module is the raster data component. This module uses the Imagerylayer class for displaying data from imagery services and offers raster functions for on-the-fly image processing. Imagery layers can be visualized using the map widget.
4. The geoprocessing module: This module is required for importing toolboxes with geoprocessing capabilities that are not part of the API but are available through ArcGIS Online. These geoprocessing toolboxes are imported as native Python modules so that you can call the functions available in the imported module to invoke these tools. The API itself also includes a rich collection of geoprocessing tools, that are available through other modules defined by spatial data type.

5. The widgets module: It provides components for visualizing GIS data and analysis and includes the MapView Jupyter Notebook widget. We'll use this widget next for visualizing maps and layers. This is not the only visualization module—the separate mapping module offers different mapping layers and 2D/3D mapping and visualization components.

As you can see, the API offers a broad range of modules for different tasks and users, ranging from publishing mapping data, performing geospatial analysis, and data manipulation. All modules use Python as the scripting language to manage GIS data and functionality. Let's now start using the API and explore some of the basic functionality before moving on to more advanced tasks.