“TYPE” is an ABAP keyword which is used to reference built-in data types of ABAP. For ex: When you use “TYPE” keyword while declaring variables as below:
FIELD-SYMBOLS <name> TYPE string
TYPES is another ABAP keyword which is used to define local types.
TYPES <variable name> TYPE STANDARD TABLE OF string WITH DEFAULT KEY
In case if your group locally defined types which can be reused across many modules then you can use TYPE-POOL.