Procedural Language/Structured Query Language is Oracle Corporation's procedural language extension for SQL. IBM supports PL/SQL for DB2 since version 9.7. Questions about PL/SQL should probably be tagged "oracle" or "db2" as well.
PL/SQL is Oracle's 3GL that provides specific syntax for the specific purpose of processing SQL commands. Since it has the same robustness, security, and portability as Oracle Database itself
- it supports the same datatypes as SQL
- it can be stored and compiled in an Oracle Database
- runs within the Oracle executable
Since V9.7, IBM's DB2 also supports PL/SQL.