You'll spend the vast majority of your time on Glip in the context of a conversation, whether it's a one-on-one with a co-worker, a conversation with a few people, or a conversation with an entire team. That's where the collaboration happens and where work gets done. There are times, though, when you need to take a higher level view of things and look at content across all of your conversations. Or maybe just browse through content in an interface tailored to each content type. This is what Glip's "apps" are for.
There is an app for each content type on Glip and they can be found toward the bottom of the left pane. Each one provides an interface appropriate for the given content type. For example, the Calendar app shows you all of your events on a calendar with day, week and month views.
The Tasks app lets you look at tasks across all conversations, with filtering/sorting options and an interface designed for project management.
TIP: Click on a heading in the right pane of any conversation to jump into the corresponding app pre-filtered to the given conversation. For example, if you click on the "TASKS" heading in the Marketing team, you'll be taken into the Tasks app filtered to show just tasks for the Marketing team. This is an easy way to jump right into project management mode.