Well, as the names suggest, the identifier of your team identifies your team - that is, your (company or personal) identity in the App Store; whereas your application identifier is unique to this application. If your team has more than one application, the team identifier for all of them is the same, but the application identifier will be different.
You can view your team ID on the Apple Developer Portal (Member Center, under the Summary account.)
The application identifier prefix usually matches the Team Team identifier prefix - both are combinations of numbers and letters assigned to you by Apple. The command identifier prefix (for example, "1234ABCD") along with the command identifier string that you select for your team (for example, "com.myteam") identifies your command in the application.
And since the application identifier string usually contains your command identifier string (for example, "com.myteam.supercoolapp"), this is the application identifier prefix prefix (= usually matches your command identifier prefix) to uniquely identify your application bundle.
In short: usually for you there is no difference in the quality of the developer. Xcode will use the correct one automatically, wherever this placeholder is used ( $(TeamIdentifierPrefix) , etc.).