Written for a small organization with limited IT and security expertise, often one generalist who owns everything.
Think of it likeLocking the doors and windows before you argue about the alarm system.
In plain English
IG1 is the floor, not a starter tier you graduate out of. Every organization is expected to reach it, and the safeguards in it are chosen to blunt the most common untargeted attacks rather than to satisfy an auditor.
IG1 covers 56 of the 153 safeguards in CIS Controls v8. Each one below links to a plain-English translation.
Control 1: Inventory and Control of Enterprise Assets