Crashlytics is used to collect crash reports if the app crashes on your iPhone or iPad. No specific user, device or location information is collected with the crash reports.
Information from Crashlytics is used to find and fix bugs which cause the app to crash.
Answers is an analytics service. It is used to show information such as how many people are using the app, what percentage are running what iOS versions etc. Answers shows aggregate information only, it does not show any specific user, device or location information.
Information from Anwers is used to help guide the future app development directions, for example deciding whether to continue supporting older iOS versions.