System engineering is integrating the elements together as a team effort to a form a structured development which will lead to production and the operation of the systems. The primary focus here is to cater to the needs of the customers and based on it build the system. And it also focuses on development cycle, documents, and validation of the system as well.
A system is basically is a construct of elements put together which do not possess the ability to work individually and perform better when put together as one single component. And these elements can be a combination of people, software, hardware and documents which are essential to be able to produce system-level results.
On the flip side, system engineering is the responsibility of creating and executing the interdisciplinary process which will fulfill the requirements of the customers and the shareholders. There is a particular acronym which is followed when system engineering is involved, it SIMILAR State, Investigate, Model, Integrate, Launch, Assess, and Re-evaluate. The end result should be of high quality, cost-effective, trust-worthy and has to be compliant for the entire lifecycle of the system.