css3 - Fluid Grid - How do I use them in Responsive Web Design? -

please forgive me, can please explain me purpose of fluid grid, featured on cssgrid, example. grid, refer columns, 9, others 12, others 24 columns...

1). grid used background, or stencil, correct sizing , positioning of divs?

2). essential fluid grid (9, 12, 24 columns) used in designing responsive website, or can use css3 , media queries define break points?

3). what's difference between number of columns, , why use 9, instead of 24 columns, example. higher column count better more content?

4). why there many fluid grid generators available? because each 1 better or different in way?

thank you

1). grid used background, or stencil, correct sizing , positioning of divs?

yes, that's more or less it. picture grid invisible stencil sizing , positioning of divs. since talking responsive design, widths of grid columns vary, depending on width of veiwer's browser window.

2). essential fluid grid (9, 12, 24 columns) used in designing responsive website, or can use css3 , media queries define break points?

grids intended simplify life, there's nothing stop rolling own solution, or mixing custom css styles off-the-shelf fluid grid framework

3). what's difference between number of columns, , why use 9, instead of 24 columns, example. higher column count better more content?

you can picture given window width, more columns = narrower columns. might find more columns gives better control given page layout, depends on specific of project. in practice, more columns give less space content because of gutter or spacing between each grid column. if thinking resoponsive design including mobile, @ point grid frameworks start displaying columns vertical stack, ie:
1-2-3
becomes
1
2
3

dividing hand-held screen 9 vertical columns isn't going usable

4). why there many fluid grid generators available? because each 1 better or different in way?

partly personal preference, may 1 option on another, , partly different features. frameworks foundation or bootstrap come lot of css styling additional javascript resources may wish use.

have fun ... it's interesting time web design!