Sitecore provides us with an opportunity to better control our config changes to Sitecore instance in the way of patching.
Imagine changing Sitecore config files for your project needs. It's all good until you need to upgrade your Sitecore solution. On upgrade, u need to compare all config files u have changed and merge changes on every config file. This is very time-consuming and confusing.
Patching helps us on upgrade, as we have not touched raw Sitecore config files. Any upgrade is easy.
Now how does patching engine works in Sitecore?
To include any patch file, u need to place that config file in /App_Config/Include folder. Patch rendering engine renders the patches in alphabetical order. So I would suggest adding a folder called zzz_projectName and add your patch files inside it. So there are fewer chances of our patches being override.
I am not going in deep here about how to patch here. But there is a great pdf from Sitecore explaining that - Sitecore Patching Guide
If you want to see the final patch version you can go to - http://hostname/sitecore/admin/showconfig.aspx
Let me know if u have any questions and I am happy to come back as soon as possible.