Difference between different query functions

Is this a trick question? I mean, the Appian documentation clearly explains the differences.

Hi [mention:59a7518e22f94dc9a0626f3f78324811:e9ed411860ed4f2ba0265705b8793d05] ,

Everything returns the same but differs in very few parameters and used similarly sometimes.

1. a!queryRecordType( recordType, fields, filters, pagingInfo, fetchTotalCount, relatedRecordData ) : Executes a query on a given record type and returns the result.
2. a!queryRecordByIdentifier( recordType, identifier, fields, relatedRecordData ) : Executes a query on a given record identifier and returns the record data.

3. a!recordData( recordType, filters, relatedRecordData, fields ) : Used mostly in Read-Only Grids, Charts, or selection components that uses a record type as the source.

I would specifically suggest you to go through documentation (added links for the functions above)  and usage considerations for each function!

Hope this helps you!!!

hi [mention:59a7518e22f94dc9a0626f3f78324811:e9ed411860ed4f2ba0265705b8793d05] 
You can go through these links 
query record type
query record by identifier
record data