Every other Website block stacks in a single column down the page. The Grid block, found in the Layout category of the block palette, is the one exception: it lays out any number of columns side by side, and each column can hold any mix of other blocks, a Heading, an Image, a Button, a Testimonial, nearly anything you'd otherwise place directly on the page. Grid requires a Creator plan, see "Free, Plus, and Creator plans compared."
Adding and filling columns
Open the Grid block's own settings panel to add or remove columns, there's no fixed limit to how many you can have. Inside a column, use its own add block control to drop in another block, pick its type from the list the same way you would from the main palette. Each block you add becomes its own row inside that column, expand a row to edit that block's content and settings directly, right there, without leaving the Grid block's panel.
Reordering a column's contents
Each row inside a column has move up and move down controls, so you can reorder what's inside a column without removing and re adding anything.
Spacing and alignment
The Grid block's own settings also include a gap between columns and a gap between rows (None, Small, Medium, or Large, set separately), a Stack on mobile checkbox (on by default, so columns fall back to a single column on a narrow screen instead of squeezing side by side), and a vertical alignment for column content (Top, Center, Bottom, or Stretch), useful when one column's content is taller than another's.
Tip: A Grid block's own Style settings, background, animation, hover effect, and container shape, work exactly the same way as any other block's, see "Hover effects, parallax, sticky blocks, fonts, shapes, and animations" for what each one does.