End Of Life – In terms of programming this refers to the life cycle of software.
For example, Joomla has EOL dates for each version : view EOL’s here.
EOL’s are important because companies can’t support each version of a software release for life, and continue to develop at a reasonable pace. Also, the most important aspect is security. When software reaches it’s EOL, it’s vital that you get off that version as soon as possible, because it’s not longer supported and may not receive security patches.
Obviously the EOL policy varies for different types of software.