Data Type

• VARCHAR2(size) : Variable-length character data
  size : minimum 1 and maximum 4000
  
• CHAR(size) : Fixed-length character data
  size : minimum 1 and maximum 2000 (slowest data type)
  
• NUMBER(p,s) : Variable-length numeric data
  p : precision , s: scale
  The precision is the total number of decimal digits, and the scale is the number of digits to the right fo the decimal point; the precision can range from 1 to 38, and the scale can range from -84 to 127
  
• DATE : Data and time variable
  
• LONG : Variable-length character data (up to 2GB)
  
• CLOB : Character data (up to 4GB)
  
• RAW and LONG RAW : Raw binary data
  
• BLOB : Binary data (up to 4GB)
  Use for pictures (multimedia files)
• BFILE : Binary data stored in an external file (up to 4GB)
  
• ROWID : A based-64 number system representing the unique address of a row in its table
  

BFILE or BLOB usually save an address or pointer of a file.