There is one kind of thing here: a page. Some pages are grouped into collections, and a collection is what most tools call a blog.
Making one
New page asks for a title. The address is suggested from the title and you can change it before or after.
Each page carries a title, an address, and an optional excerpt — the short line used when the page is listed somewhere else or shared.
Collections
A collection groups pages and lets you place the whole group on another page. Write three pieces about migrating Shopify themes, put them in a collection, and drop that collection onto your homepage: it renders as a list that keeps itself up to date as you add to it.
This is how you publish writing without configuring a blog.
Your front page
One page is the one people land on at your address. Everything else hangs off it — through your menu, through a collection you have placed, or through a direct link you send somebody.
Importing
Import HTML takes a page you already have elsewhere and pulls the text in. Formatting that has nowhere to live is dropped, which is usually what you want.