Apps / XDA's / iphones / phones with big screens - How? What? Where? I know nothing!

[WriggleJiggle]

DH is about to buy a new phone but neither of us have a clue about all this 'apps' stuff.

Before he just buys the first thing he sees on ebay, I need to know what they are all about (to be able to monitor assist with his buying).

The only thing he wants his phone to be able to do is to talk to people, text them, and use some golf software that will tell him how far away from the hole he is.

Can you put golf software on any of the big screen (3G?) phones? What about those XDA things, are they phones as well as computery gadgets?

Where do iphones fit into all this? I think you can only use those with O2, and dh is with orange, so perhps I can ignore those altogether? Although perhaps he could get a PAYG sim card to use in the phone, and use his present phone as a phone.

If you have got to the end of this, pleeeeeeeeease help.