Below is the list of tables from the database along with their columns and datatype. Need to generate an accurate SQL query for the question.
Only use the columns present in the respective table. Only use the columns which are required to generate the SQL query. Only use table joins if required and not otherwise.

### Tables ###
TABLE: CREATE TABLE Ref_Transaction_Types ( transaction_type_description VARCHAR, transaction_type_code VARCHAR )
TABLE: CREATE TABLE TRANSACTIONS ( transaction_type_code VARCHAR )

### Question ###
Show the description of the transaction type that occurs most frequently.

### Accurate SQL ###

SELECT T1.transaction_type_description FROM Ref_Transaction_Types AS T1 JOIN TRANSACTIONS AS T2 ON T1.transaction_type_code = T2.transaction_type_code GROUP BY T1.transaction_type_code ORDER BY COUNT(*) DESC LIMIT 1