Erlang
In plain terms
A language built for massively concurrent, fault-tolerant systems.
Going deeper
Erlang uses lightweight processes and message passing to handle huge concurrency with built-in fault recovery ('let it crash'). It originated in telecom for always-on systems.
Under the hood
The BEAM VM isolates processes with no shared memory, enabling hot code swapping and nine-nines reliability.
Examples
WhatsApp's backend, telecom switches, RabbitMQ, Discord (via Elixir).
Think of it like...
Like a beehive where individual bees can die without harming the colony, which keeps running.