I need significant changes to Sugar Layout, for Example ListView. Where do you change the layout?

I'm guessing I have to change the template, for example change ListViewGenetic.tpl for ListView. Is my assumption correct?

I dont understand where does the value of 'act' coming from in ListViewGenetic.tpl?

{literal}function lvg_nav(m,id,act,offset,t){if(t.href.search(/#/) < 0){return;}else{if(act=='d'){ act='DetailView';}else{ act='EditView';}{/literal}url = 'index.php?module='+m+'&offset=' + offset + '&stamp={$pageData.stamp}&return_module={$pageData .bean.moduleDir}&action='+act+'&record='+id;t.href=url;{literal}}}{/literal}

Thanks,
Tri