Google Hangouts v Hangouts Dialer v Voice : Which to download to call outbound? If I desire only to make outgoing telephone calls from my Android, which must I download?
Google Voice gives you a second phone number linked to your original. You can use it to call outbound from the app. Google voice can also recieve calls as well as send and receive texts.
Google Hangouts is a messaging app. On the web version, you can call outbound. I'm not sure about the app version. You can also use it to video call, both single person and group calls. 
^^My Google Hangouts menu^^
Google Dialer (If I have the correct product) seems to be just a phone management app, just like the typical &quot;Phone&quot; app that comes preinstalled on most phones. It gives you a dialer screen and a Google Duos video call screen as well as spam protection and caller ID. However, it doesn't look like it comes with a phone number, it uses the one from your SIM. So it'll make outbound calls, but only if you have a SIM card installed.
EDIT: Hangouts Dialer (Not Google Phone, sorry, got that wrong the first time) is a dialer for Google Hangouts (hence the name). It's a way of making phone calls without using minutes. You can call any phone number, and it shows on the receiving end the verified number connected with your device. I believe it can also be used in combination with Google Voice, using that number as your verified number.