For Xcode 10.2:
Although this question has many answers but I wanted to explain the whole concept in detail so that everyone can apply this knowledge to further or previous versions of Xcode too.
Every Xcode project consists of one or more targets. According to apple, A target specifies a product to build and contains the instructions for building the product from a set of files in a project or workspace.
So every target is a product (app) on its own.
Steps to change the name:
Step 1: Go to the Targets and open the Info tab of the target whose name you want to change.
Step 2: View the Bundle name key under the Custom iOS Target Properties that is set to the default property of $(PRODUCT_NAME)
.
Step 3: You can either change the Bundle name directly (not recommended) or if you open the Build Settings tab then on searching for Product Name under Setting you will see that Product Name is set to $(TARGET_NAME)
.
Step 3A: You can change the Product Name or you can also change the Target Name by double clicking on the target.
So changing the Product Name (App Name) or Target Name both will result into similar results. But if you only want to change the App Name and want to keep using the same Target Name then only change the Product Name.