$(header,ui)和ui = $(this);是指什么，能解释一下吗

/ ui-search 定义

$.fn.UiSearh = function(){

    var ui = $(this);

    $('.ui-search-selected',ui).on('click',function(){

        $('.ui-search-select-list').show();

        return false;

    });

    $('.ui-search-select-list a',ui).on('click',function(){

        $('.ui-search-selected').text( $(this).text() );

        $('.ui-search-select-list').hide();

        return false;

    });

    $('body').on('click',function(){

        $('.ui-search-select-list').hide();

    })

}

// ui-tab 定规

/**

* @param {string} header  TAB组件，的所有选项卡 item

* @param {string} content TAB组件，内容区域，所有 item

* @param {string} focus_prefix  选项卡高亮样式前缀，可选

*/

$.fn.UiTab = function(header,content,focus_prefix){

    var ui = $(this);

    var tabs = $(header,ui);

    var cons = $(content,ui);

    var focus_prefix = focus_prefix || '';

    tabs.on('click',function(){

        var index = $(this).index();

        tabs.removeClass(focus_prefix+'item_focus').eq(index).addClass(focus_prefix+'item_focus');

        cons.hide().eq(index).show();

        return false;

    })

}

// ui-backTop