What does a Java software developer do?

Just recently I found the article https://www.oxagile.com/article/a-glimpse-into-tizen-tv-app-development/ , and realized that there are no restrictions on the range and type of devices on which Tizen can run, which makes the OS even more promising. That is why I chose this platform for app development, because Tizen TV opens up a wide range of possibilities for creating applications for Smart TV.

What is software and mobile applications development?

Java developer primarily build APIS Using spring boot framework and some do automation using selenium and minimum do desktop app dev using java frameworks.