I purchased a speaker that can pair with bluetooth on my iphone. I was planning to play Pandora on it in the house. After I pair my iphone with the bluetooth speaker, will that speaker play any sound that comes out of my iphone such as phone calls, videos, etc? Or will the speaker only play Pandora?
It will play any sound that comes out of the iPhone, including potentially phone calls although phone calls are slightly different. Any regular (non-phone call sound) will play from the Bluetooth speaker if you are connected to the Bluetooth speaker. This includes alert sounds, sounds from videos, and basically any other sound potentially other than from a phone call. You can switch this by swiping up to the Control Center and then swiping to the left to get to the "middle" Control Center screen (at least on iOS 10) which is the "music control" screen in Control Center. On that screen, you will see a pull down menu in the bottom where you can select where the sound is currently being sent. This list will be set to the Bluetooth speaker by default, but can be switched back to "iPhone" if you want the sounds (including Pandora) coming from the iPhone. This is good for temporary switching. You can also turn off Bluetooth when you don't want it to connect to the Bluetooth speaker (if it auto-reconnects) or manually disconnect it in the Bluetooth settings (again, assuming it auto-reconnects). Obviously, none of this will help with surprise sounds (i.e. alerts) or if you forget to switch or disconnect. But, if you are done with Pandora, then you can switch or disconnect for when you say go watch a Youtube video.
As I said, phone calls are treated different. If the Bluetooth speaker is just a dumb Bluetooth speaker, then the call will only happen on the phone, either through the ear piece or speaker on the iPhone depending on whether you put the phone in speaker phone mode. If, OTOH, the Bluetooth speaker has a build-in ability to make and receive calls as some do, then the phone call sounds will happen by default on the Bluetooth speaker. Again, however, you can switch from this while on the call to switch it back to the iPhone just as you should be able to do when making a call on Bluetooth in your car. But, not all Bluetooth speakers have that built-in ability. For example, an Amazon Echo can act as a Bluetooth speaker, but it will not deal with calls at all (I could not find a way to switch into such a mode either as an Echo does have a mic, so in theory it could act as a speaker phone for the iPhone). It is just a "dumb" Bluetooth speaker with no call functionality.
The one potential wrinkle is whether the Bluetooth speaker will auto-reconnect when it is powered back on or you come back in range if you do not manually reconnect. I cannot easily test the first with my Echo (it does not have an easy power off button...you turn it off by unplugging it), but I can with the second. If I get motivated, I will test that. If you do have to manually disconnect when done using the speaker, it is not hard to do. If you have no other Bluetooth devices, then the easiest way is to just turn off Bluetooth on the iPhone, which is really easy to do. If you have other Bluetooth devices (say an Apple Watch like I do), then you can go to the Bluetooth setting and manually disconnect from just the Bluetooth speaker. That is only a few "taps" to do. Of course, you then will have to manually reconnect to the Bluetooth speaker when you want to use it again.
Also, will the pairing with the house speaker affect my iphone's connectivity with my car? Will still be able to make and take calls from my car with my iphone? In other words will I have a separate set of pairings for my car and for the speaker in the house? Will one pairing reset the other and can they both exists on my iphone at the same time. I hope my question is clear, .
Pairing with the Bluetooth speaker should not affect how your iPhone pairs with you car the vast majority of the time. iPhones (and many other smartphones) can have an active connect with multiple devices at a time. When I am in my car, my iPhone is connected with my radio, my Apple watch and at least two other devices. And you can pair with tons of not actively connected devices. My iPhone is paired with more than 10 devices, most of which are not typically "active" (i.e. my car is turned off when I am not driving it, so the radio and another device in the car cannot actively connect to my iPhone; there are at least three Bluetooth devices in the house that are paired but deliberately unconnected from until I need/want to use them; and my one set of Bluetooth headphones that would auto-reconnect if when they are powered on, but are not powered on when not in use so are paired but not connected most of the time since they are powered down; etc).
The one potential way they might interfere, so to speak, would be if you get in the car and start it up while you are still in range of the Bluetooth speaker while it is powered on and still connected to the Bluetooth speaker. At that point, I am not sure if you would connect to the Bluetooth in the car or not (never tried having my iPhone actively connected to a Bluetooth speaker when I got in the car to see what happened, so not completely sure what would happen...if I get motivated, I might try it assuming that I can stay connected to the Echo when in the car...the Echo is my only Bluetooth speaker) and even if you did, the iPhone might be set to use the Bluetooth speaker for sounds. That likely will be automatically "cured" when you drive away from the house (assuming you are NOT bringing the Bluetooth speaker with you while it is powered on) and go out of range of the Bluetooth speaker. More than likely, the iPhone will automatically switch over the car's Bluetooth, but I am not 100% sure. There is also the fact that Bluetooth does not have great range, so depending on where the Bluetooth speaker is in the house (again assuming you are not bringing it with you while powered up) and assuming you leave it powered on, you might lose the connect when you go to your car anyway.