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A filter's Comparison Type is defined during the creation of the filter:
Creation of a filter
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This Comparison Type is unique. All Filters with a FreeText Comparison Type are gathered into a single filter with an ID of "freetext".
Here is an example to help you grasp the concept:
A search with a single free text filter:
And to keep it simple, the DAM Center, which I am using, only has one asset:
The title of the asset is "Hydrangeas".
Because the search only has one free text filter, the string, which the parameter is compared to, will be "Hydrangeas".
The asset has two keywords: "flower" and "summer", so if you were to add a Keywords free text filter, the string, which the parameter is compared to, will be "Hydrangeas flower summer", ie "Title Keyword Keyword".
The asset has a description of "pretty flower", so if you were to add a Description free text filter, the string, which the parameter is compared to, will be "Hydrangeas flower summer pretty flower", ie "Title Keyword Keyword Description".
The "comparison" is a Contains function, ie the filter will return any assets, whose "free text string" contains the parameter, eg a parameter of "flower" will return the asset. The parameter "flo" will not return the asset. However, the parameter "flo*" will return the asset; as will the parameter "*wer".
Due to the inner workings of how such filters work, any search, which has a freetext filter MUST be populated (see UseSolr for a guide on how to populate a search).
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Equals
Tests whether a Filter's parameter matches exactly with the data, the filter works on.
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