Slack app vs Slack bot: what's the difference (and which do you need?)
A Slack app is the installable package: identity, scopes, marketplace listing. A bot is a user inside that app that posts messages and responds. You install an app; you see its bot in channels. For PR notifications you install an app whose bot posts the updates.
What is a Slack bot?
A bot is a special user account that apps use to post messages, react, and respond. It is what you see in the channel member list with the APP badge. On its own it does nothing - it belongs to an app that defines what it does.
What is a Slack app?
The app is the container: OAuth scopes (what it may access), slash commands, incoming webhooks, event subscriptions, and optionally a bot user. Apps are what you install from the Slack Marketplace or via an Add to Slack button. Permissions belong to the app, not the bot.
Which one does your team need?
You never install 'a bot' - you install an app that includes one. Practical guide: want PR summaries in a channel, install a notifications app like HotBot. Want a quick internal post from a script, an incoming webhook is enough. Want slash commands and interactivity, that is a full app with a bot user.
Can I use a Slack bot for free?
Yes. Free Slack workspaces support apps, and most developer tools have free tiers. HotBot's free tier covers 3 repositories, 1 messaging provider, and 2 schedules - enough to run digests for a small team. Watch app counts: every app adds integrations to manage, so prefer fewer apps that do more.
How are Slack bots built?
Usually on Bolt (Slack's frameworks for Python, JavaScript, and Java) or a webhook receiver. But most teams should not build one for PR notifications - installing a maintained app gets you filtering, formatting, and edge cases handled. Build when the behavior is unique to your workflow.