Compressing is an Esri feature that helps reduce the size of a file geodatabase by finding repetitive patterns in the database and grouping them together. This is a different concept than compacting, which we will also address later. For example, if you have your Food_and_Drinks feature class with 10 features, and all of them have the RATING field set to Good, compressing the feature class will count the Good values and add the number of occurrences as Good(10). When this feature class is accessed, the data is unpacked again and queried as desired. You might think that the processor needs to perform some work before querying and therefore, this might slow down the performance. However, with the advanced microprocessors and multithreading, this little extra work is barely noticeable.