Yeah, Slack makes this harder than it ought to be.
If you're on mobile, tap the name of the channel to see the topic and description.
If you're on desktop, the topic is visible at the top, and you can click the channel name to see the description.
We also have a
Member Handbook. Every new member joining the slack should be sent a message explaining that this handbook describes how we use slack — and you'll find detailed channel descriptions on that page.
Hope that helps!