Css classes l_column, .l_beam, .l_grid, .l_width-limited and .l_superimposed are the most commonly used. See scss/5-layouts/ for more.
Each of these can be appended with a variety of other classes, from middle, right, middlev, bottom, space-between etc. to l_beam--wrap, l_grid--twin, l_grid--auto etc. to distribute and divide the grid container to your preference.
