The sidebar (or the menu button on mobile) is how you get around Chillverse. Here's what each section holds:
Dashboard takes you back to your home base. Streak shows your daily activity streak.
Games is a group with two destinations: Play Games, where all the mini-games live, and Exploration, the 3D world you can walk around and search for rare items in.
Mall is also a group, covering Shop — where you spend diamonds on cosmetics — and Inventory, where everything you've unlocked or bought is stored.
Gift lets you send a cosmetic item to another player directly. Ranks shows your current standing and how it's calculated. Achievements tracks your overall milestones and badges across the whole app.
Profile is a group containing your Profile page (what other players see about you) and your Wallet (your diamond balance and purchase history).
Settings is the last group, holding Settings itself (account and app preferences) and Version (Chillverse's upgrade/cosmetic tiers, unrelated to your subscription plan).
Sections shown as a group (like Games, Mall, Profile, and Settings) expand when you tap them, revealing their sub-pages underneath.