Not long ago, essentially all software-development processes followed the same, basic approach. The software would go through various development phases, including implementation, testing, revising, etc., until it was eventually ready to be deployed to the customer. And while there would naturally be some need for ongoing maintenance or after-release patches, essentially the entire product was developed upfront and in its entirety, before the end user ever had the opportunity to encounter it.
Unfortunately, this meant excruciatingly long development cycles, and often led to a poor customer experience — after all, if the released product is not fully up to user expectations, returning to revision and testing phases can be difficult and time consuming, leaving customers unfulfilled.
Continuous development is a solution to these issues. Part of the Agile methodology, and incorporating many DevOps processes, continuous development works in smaller increments and allows software teams to release their products quickly, making continuous, ongoing improvements after deployment.