One of the most common questions I've come across over the last year or so - both from teachers who have asked it, and from speakers and writers who have answered it is 'What is mobile learning?' (also referred to as m-learning).
I've always had a very simplistic view of what it is: learners might use their phone, or iPad, or PlayStation Portable, or whatever it might be to use or improve their English. I don't think we need long explanations to understand that. Examples are good though: a teacher might ask their students to talk about a photo on their phone, or to record something for homework. You can find more examples here: http://www.teachingenglish.org.uk/tips/mobile-learning
Learners themselves can benefit from guidance with examples too. There are tools to help them - not least the British Council's own learner apps: http://learnenglish.britishcouncil.org/en/mobile-learning As a language learner myself though, the best aid I've come across is called Evernote.
If you've not heard of Evernote, I'd recommend trying it out and/or suggesting it to your students. It's not aimed specifically and language learners, but it's really useful. Basically, it allows you to save ideas, texts, examples of language, recordings, photos, etc. on your computer, phone or pretty much any mobile device. Everything is synced, so a photo you take on your phone will also appear on Evernote on your PC.
For me it's become a way of organising my Polish language learning. I like the tags function, which means if I take a photo or record a friend asking for something in a restuarant, I just tag it 'restuarant' and it I can later on find it when I browse through all items with that tag. It is, I think, like a modern version of vocabulary cards: I remember advising students to write things down on small cards then look at them on the bus or when they had a spare 5 mins. They can do the same much more effectively with Evernote. Try it!