Your question is somewhat broad, but to develop software with books like Pressman , a life cycle must be respected that is summarized by:
Analysis
Design
Coding
Tests
Implementation
Personally, I think that to develop software or at least to be a complete professional you must know all the stages, although the objective is to be a software developer, understand the:
Analysis : It is useful to try to understand what you really want to do, regardless of how it is done.
Design : To find the best way to do something, once the "something" is already defined.
Coding : In this section, you would enter knowledge about the tool (programming language).
Testing : Once the software is developed, understand how it can be seen to work correctly in all possible scenarios.
Although it is boring, I recommend you read some Software Engineering book to have a starting point in the subject.
Greetings.