Columns of user's tables, views and clusters
Columns
   ___________________________
 
   TABLE_NAME
      Table,view or cluster name
   COLUMN_NAME
      Column name
   DATA_TYPE
      Datatype of the column
   DATA_TYPE_MOD
      Datatype modifier of the column
   DATA_TYPE_OWNER
      Owner of the datatype of the column
   DATA_LENGTH
      Length of the column in bytes
   DATA_PRECISION
      Length: decimal digits (NUMBER) or binary digits (FLOAT)
   DATA_SCALE
      Digits to right of decimal point in a number
   NULLABLE
      Does column allow NULL values?
   COLUMN_ID
      Sequence number of the column as created
   DEFAULT_LENGTH
      Length of default value for the column
   DATA_DEFAULT
      Default value for the column
   NUM_DISTINCT
      The number of distinct values in the column
   LOW_VALUE
      The low value in the column
   HIGH_VALUE
      The high value in the column
   DENSITY
      The density of the column
   NUM_NULLS
      The number of nulls in the column
   NUM_BUCKETS
      The number of buckets in histogram for the column
   LAST_ANALYZED
      The date of the most recent time this column was analyzed
   SAMPLE_SIZE
      The sample size used in analyzing this column
   CHARACTER_SET_NAME
      Character set name
   CHAR_COL_DECL_LENGTH
      Declaration length of character type column
   GLOBAL_STATS
      Are the statistics calculated without merging underlying partitions?
   USER_STATS
      Were the statistics entered directly by the user?
   AVG_COL_LEN
      The average length of the column in bytes
   CHAR_LENGTH
      The maximum length of the column in characters
   CHAR_USED
      C is maximum length given in characters,B if in bytes
   V80_FMT_IMAGE
      Is column data in 8.0 image format?
   DATA_UPGRADED
      Has column data been upgraded to the latest type version format?
   HIDDEN_COLUMN
      The column exists in the table but cannot be selected. (mostly for internal use)
   VIRTUAL_COLUMN
      The column is an Oracle 11g Virtual column.
Example
select column_name, data_type, hidden_column, virtual_column from user_tab_cols where table_name = 'MY_XML_TABLE' ;
Related:
DBA_ALL_TABLES ALL_ALL_TABLES USER_ALL_TABLES DBA_PART_TABLES ALL_PART_TABLES USER_PART_TABLES DBA_TABLES ALL_TABLES USER_TABLES TAB DBA_TAB_COLUMNS ALL_TAB_COLUMNS USER_TAB_COLUMNS DBA_TAB_COLS ALL_TAB_COLS USER_TAB_COLS DBA_TAB_COL_STATISTICS ALL_TAB_COL_STATISTICS USER_TAB_COL_STATISTICS DBA_TAB_COMMENTS ALL_TAB_COMMENTS USER_TAB_COMMENTS DBA_TAB_HISTOGRAMS ALL_TAB_HISTOGRAMS USER_TAB_HISTOGRAMS DBA_TAB_MODIFICATIONS ALL_TAB_MODIFICATIONS USER_TAB_MODIFICATIONS DBA_TAB_PARTITIONS ALL_TAB_PARTITIONS USER_TAB_PARTITIONS