Alice,
You've received lots of good suggestions so far, and I have a few comments to add as well. I'm also from an "older generation" that didn't grow up with cell phones, but I've had one and travelled with one for many years, and have found it to be indispensable. I often travel solo and there's no way I will ever travel without one again.
As you mentioned "Apps" and "take photos", it sounds like you're referring to a smart phone rather than a more "basic" model. A few thoughts.....
PHONE
- There are two main operating systems, Apple and Android, so you'll have to decide which one you might be more comfortable with. If you use other Apple products, you may find it more practical to stick with that ecosystem. I've used an iPhone for many years, and I'm very pleased with it.
- Memory - I would suggest buying as much memory as you can afford. Some phones start at 128GB (or lower), but I'd suggest at least 256 GB.
- There is some merit in the suggestion to buy the phone at home, so that you can become familiar with it and download any apps that you want. However if you do that, you'll also have to choose a carrier that will provide a good, inexpensive roaming plan for Switzerland. Since I don't live in the U.S., I'm not overly familiar with the plans offered by cell networks in your area. Some travellers keep the cellular roaming switched "off" whilst in Europe to reduce costs a bit, and use only Wi-Fi. Using Wi-Fi in public places can be "risky" so I prefer to use cellular data most of the time. However I've found that having data roaming provides much more flexibility and I'm willing to pay for that.
- Always back your phone up, either to a computer or "the Cloud". The sales people at the cell shops can explain that.
APPS
It's difficult to answer the question on "what Apps you must absolutely have". Initially you'll probably only want a few specific to the trip, but as you become familiar with the phone you'll probably want more Apps for specific purposes. Some of the Apps that I've found very useful for travel....
- Google Translate - I don't speak any language fluently other than English. Even though it doesn't always provide perfect translations, I've found GT very useful.
- Google Maps - that's been useful on a many occasions when I've been lost when wandering around cities.
- Airline App - I have the apps for the airlines I primarily use for flights to and within Europe, and those are good to have.
- Rail Apps - I have several rail apps on my phone, including Trainline as well as the SBB and DB apps. Those are useful for not only checking schedule times, but also for booking tickets.
- Bank apps - I have apps for the financial institutions that I deal with so that I can monitor activity on the accounts during trips. I've always used either credit or ATM cards during travels, but may use the phone for transactions on future trips. I also have the XE currency exchange app which I reference at times.
- E-mail - I use the built-in app for that.
- Text messages - I primarily use the built in Apple text app most of the time, but two of my contacts use Viber so I have that too.
CAMERA
- I concur with a previous reply to become familiar with the camera before the trip. Smartphone cameras have improved a lot in the last few years. Although they're very easy to use, getting the best results will require some practice.
- Try to choose the proper phone orientation for the subject. Many people use "portrait" mode (phone vertical) for most shots, however some would be better if the camera were in "landscape" mode (phone horizontal).
That's all I can think of at the moment. Good luck with your decision!