What are theme styles?
A theme style (Shopify and many theme teams also call this a preset) is a ready-made set of global design choices we have created for you: typography, color defaults, and other theme-wide settings. It is not a different theme and not a separate app—it is a starting look you can select or build on top of.
All styles in a theme use the same sections and features; only the bundled defaults differ. You can still change everything in Theme settings after you pick a style.
In the theme editor (what you see in your store)
In Customize → Theme settings → Theme style, you can preview the other styles that ship with your theme and use Change style to apply one. That is the same control whether you first found the theme from a “Cafe”-style listing or a “Blockshop”-style listing in the store: the editor lists every preset that belongs to that theme.
Shopify’s help centre explains theme style in more detail, including that applying a style updates your current global settings (for example colors and fonts) to match that preset. Your store’s products, collections, and pages are not removed; if you are unsure, duplicate the theme in Online Store → Themes before changing style so you keep a copy of your current look.

In the Shopify Theme Store (how discovery changed)
The Shopify Theme Store used to group several looks under a single theme page. Now, each demo (preset) is often shown as its own listing so you can search and open the exact look you want, with links on that page to the sibling styles in the same theme family.
Important for buying and installing: you still add one theme to your store. A purchase or trial of that theme includes all of its styles. You do not need to buy each store listing separately to use another style in the pack—after the theme is in your admin, switch styles from Theme settings → Theme style as above.
Some themes also install or preview with the preset that matched the listing you chose, so your first view may match that demo; you can change to any other style in the same theme from the theme editor at any time.