A materialized view inherits both properties from tables as well as views. Similar to a regular view it has to have a original table from which it retrieves its data and to which it is connected. Similar to a table it includes real data instead of just the algorithm which calculates the data.
Visualization in QGIS
Materialized views should be preferred over regular views when it is intended to visualize the data, for example in a GIS, since regular views have to constantly recalculate their data when visualizing it and therefore cause performance problems.
When creating a materialized view which holds geometry data, it is important to create a unique index on the ID column. QGIS requires this unique index to properly display the data.