Salesforce1 is a new mobile application provided by Salesforce.
There were previously a few different ways to connect to Salesforce using a mobile (iOS or Android - iPhone, iPad, Android tablet, etc.) device: Salesforce Classic, Salesforce Touch, and Chatter Mobile. This mobile application replaces the most recent application, Chatter Mobile, which has been renamed to Salesforce1 and updated with a ton of incredible new features.
Summary: What is it?!
The Salesforce1 announcement page describes it as:
Say hello to the Salesforce1 Customer Platform.
Connect all your apps. Connect all your devices. Connect all your customer data. All with one Customer Platform designed for the new hyper-connected world of customers. With new APIs, mobile tools, and more, it’s everything you need to sell, service, and market like never before.
And, here's a summary from the announcement video:
"Introducing Salesforce1 - an all new platform engineered to connect customers to the next generation of apps and devices, so you can sell, service, and market like never before. A customer platform designed entirely to accelerate development and deployment in a mobile first world. With social collaboration at its core and 100% Salesforce cloud. So not only are you ready for what's next, you're way out in front of the next. Here you'll find APIs for anything; so you can connect to everything. A world class mobile AppExchange, so you're instantly ready to build and sell next generation apps for the enterprise app revolution. Plus a new Admin app, so you can quickly change things on the fly. This is where one button instantly connects everything: your customers, your employees, your partners, your products, everything you've ever created on Salesforce, and everything yet to come."
Why would I use Salesforce1 and what can I do with it?
It's probably easiest to think of Salesforce1 as a new mobile interface for everything in Salesforce (except development, for now...). So, it's used to access Salesforce on mobile devices. It's possible to access all Standard and Custom objects, and it even makes it easy to publish a Visualforce Page to mobile devices. To do so, follow these quick instructions:
Navigate to Setup > Administer > Mobile Administration > Salesforce1
Make sure Salesforce1 is enabled and click Save
Navigate to Setup > Build > Develop > Pages and select a Visualforce Page
Click "Edit", check the "Available for Salesforce mobile apps" checkbox; then, click Save
Navigate to Setup > Build > Create > Tabs
Create a new Visualforce Tab for your Page
Check the "Mobile Ready" checkbox and click Save
Navigate to Setup > Administer > Mobile Administration > Mobile Navigation
Add your new Visualforce Tab to the Salesforce1 Navigation Menu
Go to [your-salesforce-instance-domain].salesforce.com/one/one.app to test (I'd recommend using Chrome, because I couldn't get it to work properly in Internet Explorer or Firefox)
New APIs??
The documentation has more information on how to develop mobile ready Pages and integrate other services. This is where the APIs come in. Most, if not all of the APIs listed, were released before Salesforce1. However, any API that could be used in Salesforce previously can now be used with Salesforce1 as well.
From the comments, it appears that the only relatively new API is the Analytics API which was made generally available in Winter '14.
Analytics API Developer Guide - Analytics REST API gives programmatic access to integrate reporting into a wide variety of applications. You can get report metadata, run reports synchronously or asynchronously to get summary data with or without details, filter...
All previous API documentation can be found on developer.force.com.
As a side note, I'd highly recommend taking a look at the salesforce Mobile app Design Templates to implement a mobile look and feel for your Salesforce apps.
What about ____? (Or, where can I get more information?)
Check out the official announcement page or the Salesforce1 Platform API Services Guide for more information. Also, keep checking Dreamforce's YouTube page for videos of the Keynotes and Sessions where Salesforce1 was announced.
