Slack signs its requests using a secret that's unique to your app. With the help of signing secrets, your app can more confidently verify whether requests from us are authentic.| Slack API
Slash commands allow users to invoke your app by typing a string into the message composer box. By enabling slash commands, your app can be summoned by users from any conversation in Slack. Slash commands created by developers cannot, however, be invoked in message threads.| api.slack.com