Monolith
In plain terms
An application built and deployed as a single unified unit.
Going deeper
A monolith houses all functionality in one codebase and deployment, which is simple to start with but can grow hard to scale and change. It's the opposite of microservices.
Under the hood
Easier to develop/deploy early; modular monoliths keep boundaries clean as a middle ground before splitting.
Examples
Early-stage apps, modular monoliths, Rails/Django apps, Basecamp's stack.
Think of it like...
Like one big all-in-one department store versus a mall of independent shops.