Software Engineering and Software development does not mean the same thing. Software engineering is the establishment and use of sound engineering principles in order to economically obtain software that is reliable and works efficiently on real machines. Software development is, of course, part of software engineering. You may find few software engineers are involved in software development, but not all developers are engineers.
A software engineer involve in software development through connecting the client's requirements with applicable technology solutions. They provide systematically developed solutions and process to provide required functionalities. On the other hand, the software developers are the driving force. They are responsible for the development process and collaborate with the client to create design. Then they have programmers to write the code to run the program properly.
In many cases, the client approaches developers to create a piece software. If they are not experienced enough or not knowing the difference, they start making code without proper design. If the project is big and have multiple modules linked and depend each other, it could reach a poit where it is very dificult to make changes. "If a code is not maintainable, it will be removed eventually". If proper maintainance or changes are not possible, either the product reach a point where its a waste of time, energy and money to make changes called "technical debt" or eventually get replaced by better code.
We engineer the product. The team of engineers do a thorough system study, architect the product applying engineering principles, finalizes the most suitable technology, form a team that is best fit for the chosen technology and develop the product. Unit testing and integration testing are embedded from the very beginning of engineering process. We follow Agile Methodology, Scrum, test driven development(TDD), Extreme Programming (XP) and more. This helps us to deliver products with almost no known issues, ahead of schedule.
As we all know, software applications can malfunction. While engineering, we take utmost care and consider all possible exceptions. We look into every problem to its deepest root and engineer the product.
In case if the software malfunctions, we study the (odd) behavior, find the root cause and fix the cause by re-engineering the product and make sure the exceptional cases are handled appropriately. We never fix bugs, instead we re-engineer the product and take care of the real cause of problem
We take the vision which comes from dreams and apply the magic of science and mathematics, adding the heritage of our profession and our knowledge to create a design.