Apache Maven, or more commonly known as just "Maven," is an important tool for Java programmers. It allows you to build your project, manage dependencies, generate documentation, and a lot more. I can vouch for Maven's usefulness because I have come from the pre-Maven world of Software development, where you need to manage all the JAR files required by your project. It may seem easy to you that just download the JAR file, but it's not so easy in practice. For example, you added a new library in your project — say the Spring Framework, which also needs log4j, but you thought log4j is already there, so you didn't do anything, only to realize that your application is not starting anymore and throwing long and convoluted errors. This can happen because of version mismatch, like Spring needed a higher version of log4j than available in your project.
This is just a tiny example that shows how manually managing dependencies can create nightmares. Maven took away all those pain by not only automatically downloading those JAR files for you but also created a central place, known as a Maven repository, to store those JAR files for better management.
Maven is not just a dependency management tool; it's, in fact, much more than that. The biggest advantage of using Maven is the following convention, which makes software development easy.