What does the software Spring do exactly?

I have to work with Spring for a task and I’m not entirely sure what it does. I just know it is a dependency injection program which will give me the tools I need to complete the task.

But I’m getting confused because in my head I thought I had to download things the usual way but it seems to me all I need is this Spring application and it will have the tools I need inside it? So is it like a program that has multiple tools within it?