Meaning of implementation project(':urbanairship-fcm')

I was reading https://github.com/urbanairship/android-library and I found this:

dependencies {
    ...
    // Urban Airship SDK - FCM
    implementation 'com.urbanairship.android:urbanairship-fcm:9.7.1'
}

In the sample project at https://github.com/urbanairship/android-library, they are using this:

dependencies {
    ...
    // Urban Airship - FCM
    implementation project(':urbanairship-fcm')
    ...
}

I was expecting the sample project to have implementation 'com.urbanairship.android:urbanairship-fcm:9.7.1' and not implementation project(':urbanairship-fcm'). Is 'project(:urbanairship-fcm') referring to a folder that contains the urbanairship-fcm library/code? Is it referring to this folder?: https://github.com/urbanairship/android-library/tree/master/urbanairship-fcm

Thank you.

UPDATE 1: Basically, I am familiar with this syntax: implementation 'com.urbanairship.android:urbanairship-fcm:9.7.1'. I am not familiar with this syntax: implementation project(':urbanairship-fcm'). If I understand it correctly, implementation project(':urbanairship-fcm') means that there is a folder called urbanairship-fcm that contains the source code with the com.urbanairship.android:urbanairship-fcm library. Is that correct?

When you see implementation project(':urbanairship-fcm') that means it's pulling it from a local module instead of remote package. The sample is setup to use the library source so we can use the sample app to test our development changes.