In the Markup Framework, layouts are a separate thing from grids. Layouts define the basic structure of a Web page, while grid systems are meant to be dropped in to individual zones within an existing layout, to help set out the content within that zone.
This makes layouts more flexible. Multiple responsive breakpoints are possible, something that is tricky to achieve with generic grid structures.
A range of one-, two- and three- column layouts are included in the Markup Framework.
All layouts are responsive, scaling "mobile first" from a simple one-column layout for small screens, to multi-column layouts for larger displays.
Layout style sheets also define which parts of a Web page get printed, and which do not. Typically the content zones get printed, while headers, footers and navigational zones do not get printed.
View the layout demos here.