Anonymous Blocks:

An Anonymous PL/SQL blocks can be embedded in an OCI program or Oracle Precompiler. At run time, the program, lacking a local PL/SQL engine will sends these blocks to the Oracle Server where they are executed and compiled. Similarly, interactive tools like as lacking a local PL/SQL engine, SQL*Plus and Enterprise Manager, must send anonymous blocks to Oracle.

Named Blocks:

Named blocks act in the similar way as anonymous blocks except in which they can have names in the form of labels that are valid only for that program.