This is before the runes where added so my context is for the version before that. I’ll have to update this to state what version.
You’ll notice a simple pattern that you can follow. .svelte is the html template, .js is for supporting front-end code and .server.js is for server side rendered code.
+page
+page.svelte
+page.js
+page.server.js
+server
+server
Receiving data
Content negotiation
+error
+layout
+layout
+layout.svelte
+layout.js
+layout.server.js