When you create a workflow, you can choose among various workflow steps to document your internal processes. Integrations enable powerful capabilities of some of the workflow steps.
For example:
File upload, for assignees to upload files from Box or Google Drive (e.g. for uploading HR documentation or project files).
Create a task, to trigger automated creation of a task on a project management tool (e.g. creating a task on Asana, issue on JIRA, or card in Trello, when a specific workflow step has been completed)
Post to channel, to trigger an automated notification to a Slack channel (e.g. to notify project members that a specific workflow step has been completed).