A template is a piece of pre-built page structure that someone (often a developer or site admin) has saved separately. When you apply a template to a page, the page gets the template's structure overlaid: some blocks are fixed and can't be edited, some can be edited but not moved, and some are open slots where you fill in your own blocks.

The editor has two modes when a block is selected: text mode (you're editing inside the block) and block mode (the whole block is selected as a unit).

The link picker, image picker, and upload dialog are part of Hydra's chrome — they look the same on every site. What varies by design system is which links and images are click-to-edit in the preview: a site might wire up every link inline, or only a few "primary" links, with everything else editable from the sidebar. Same applies to images.

Click into any text in the preview that's marked inline-editable and start typing. There are two kinds of text fields: simple text (like a title) and slate (rich text — the body of a paragraph block, descriptions, etc.).

A container block holds other blocks inside it — sliders, columns, accordions, grids, generic sections. The blocks inside are called its children. Containers can be nested (a column inside a row inside a section).

The block chooser, slash menu, and drag handles are part of Hydra and look the same everywhere. What you can pick from those choosers — the list of block types — comes from your site's design system. One site might offer "Lead paragraph", "Pull quote", "Stat highlight"; another might just have "Text" and "Image". Mechanic is identical.