what is the use of a "PRE" tag in (X)HTML

It's for displaying data/code/art where you want all your spaces and newlines to be displayed as is, and want your columns to line up. So you can do stuff like this:

+-----+------------------+--------+------------+
| id  | session_key      | length | expires    |
+-----+------------------+--------+------------+
| 263 | SNoCeBJsZkUegA7F |  86400 | 1257401198 |
| 264 | UoVm3SZRmPHnac4V |  86400 | 1257405561 |
| 262 | bjkIOWBhI1qxcrWr |  86400 | 1257401189 |
+-----+------------------+--------+------------+

without "pre" or "code" or some such, this looks like this:

+-----+------------------+--------+------------+ | id | session_key | length | expires | +-----+------------------+--------+------------+ | 263 | SNoCeBJsZkUegA7F | 86400 | 1257401198 | | 264 | UoVm3SZRmPHnac4V | 86400 | 1257405561 | | 262 | bjkIOWBhI1qxcrWr | 86400 | 1257401189 | +-----+------------------+--------+------------+