I have a simple Salesforce application consisting of 2 visualforce pages and their controllers. They are calling a webservice. It is running fine on laptop. Now i want to use application on my mobile as an app. Can it be converted. If yes, how? If not, Please tell me where should i start building. I am messed up in App Cloud, Salesforce1 and Lightning. These all can be used for mobile dev. But i dont know the difference.
1) The simplest approach is to mobilise your existing Visualforce pages. You can do so by making your VF pages responsive using a framework such as Bootstrap, Foundation etc. This will ensure that your pages load in an optimal manner on mobile devices.
2) Once you've done that, you would typically want to make your VF pages more easily accessible on mobile devices. e.g. Users need not type the full page URL - for that you you should enable your VF pages in Salesforce1. For that, follow the steps mentioned here.
3) The other option is to refactor your VF pages to use lightning components and expose them as a Lightning application. You can follow this tutorial to do this.
My suggestion would to be to start with Steps 1) and 2) - that's the minimum you need to 'mobilise' your VF pages so they are easily accessible on mobile. Once you're ramped up on Lightning, you can consider migrating your VF pages there.