Character functions analyze and modify the contents of CHAR and VARCHAR2 string variables.

Numeric functions are a full range of operations that manipulate numbers, including trigonometric, logarithmic, and exponential functions.

Date functions are utilities that allow programmers to perform high-level actions on date variables, including date arithmetic.

Conversion functions convert from one datatype to another, often formatting the output data at the same time.

LOB functions allow operations on LOB (large object) data.

Miscellaneous functions perform operations that don't fall into any of the other categories.

Example of built in functions:

1. to_date - a convertion function that will convert a string date to a date datatype

2. sum - a group function that will return the summation of all values in the column

3. upper - a single row function that will return all characters in a column in upper case