How are cool app that store all data on the Internet, like Kik or Instagram, made? What software and hardware do they use?
Step one: think up a cool idea.
first, decide which programming language you are comfortable with,
then determine which mobile OS support that language,
google search for the developer community of that mobile os,
and there will be instructions on how to install the IDE and necessary tools for that language,
also, most developer communities have a sample section which allows you to check out and build your first few apps.
I'm not being rude, but
Numero Uno- Get a job at Google.
Step Two- Ask them.
I believe that's a question only someone technically involved with those services can answer. As for instagram you are actually lucky enough as there is a blog post outlining some of the details.