Why would you need to use a Layer 3 switch? What instances would it be required?

Hey everyone,

First off I probably know enough about networking to be dangerous. Treat this as if I know nothing, lol.

I was told that I need a Layer 3 switch for my project. We are going to use a Cisco 3750 that we can get from a refurb vendor online and it's already been purchased.

When I suggested we use a Cisco 2960 switch, I was told this wasn't Layer 3 and therefore it wouldn't work for our application.

In my application, the Cisco switch will be on XXX.XXX.1.100, and all the devices it will connect to will be on XXX.XXX.11.1, XXX.XXX.11.2, XXX.XXX.12.1, XXX.XXX.12.2, and so forth.

Why would you NEED to use a Layer 3 switch? What instances would it be required?

Please help educate me, and if you have any links or info handy I'm all for it. Just looking to learn from people much smarter than me.

Thanks!