I know the feature is there under Location Services but I never really thought about this. Might be a newbie question, but do I need to download and keep the app?
The app is another way, in addition to the web app when iCloud.com is accessed from a computer, to locate a device on which Find My [Device] has been enabled. Both methods still require signing in with an iCloud AppleID.
I know the feature is there under Location Services but I never really thought about this. Might be a newbie question, but do I need to download and keep the app?
Nope. The App is only used to locate another device. So unless you have other Apple hardware you might be trying to find there is no reason for you to even install the app at all.