There are a lot of definitions to software engineering, most of them are applicable and some of them are not (in my opinion)
The most applicable one in my opinion is : Software engineering is the process of developing high quality software in time and within the pre-defined budget to meet the user real needs.
Let’s look at each term briefly :
1- “The Process” :
There are a lot of processes approaches in software development and we can’t say that one is better than the other and nobody can stick with only one of them, because each type of projects has different approach that is better to be used with.
2- “High Quality” :
The most important question here is : what is “Quality” and how to ensure it in any software ??
There are many books and researches out there dedicated to answer this question. In brief I will say that there are many aspect of quality in softwares like reliability, efficiency, portability, …. etc.
You can read more about software quality here.
3- “In Time and within Budget” :
One of the most important task in software engineering is to define a plan for the software development such that it will be delivered to the customer to released to the market before the dead line. And as you know “Time is money”, this is highly applicable in software development as the most expansive thing in this process is the human resources and their salaries. So, there must be a good management to minimize the work done by them.
4- “Meet the User REAL Needs”
In my opinion, this is the absolute most important purpose in software engineering. Because there is no point in developing a software that no body is going to use. But, why is the word “Real” ?? it is there because most of the users and customers do not actually know there needs and it is the job for the smart software engineer to figure it out.
That was a brief answer to the question (what is software engineering ??), and there is a lot to know about it. Each point that I have talked about is a whole big topic by itself and there are a lot of books about each of them.
Best Regards,