Facebook launched a mobile messaging application for Apple's iPhone and Android devices. Facebook engineer Lucy Zhang said Facebook Messenger can be used to exchange messages with Facebook friends but also with other people in a user's telephone contact list.

Zhang, in a blog post, highlighted Messenger's group messaging capability. "When you're on the go, coordinating a bunch of people can be tricky, especially if plans change at the last minute," she said. "With Messenger, you can quickly start a group conversation and message everyone at once."

Facebook said Messenger also has location- and photo-sharing features.  "If you choose to add your location, the people you're messaging with can easily find each other on the map," Zhang said. "You can also attach photos, so everyone else can see and comment on what you're looking at."

Messenger integrates text messages, instant messages and emails. Zhang is a co-founder of Beluga, a startup founded by former Google employees that allows users to send group messages to family or friends. Facebook acquired Beluga in March.