Описание тега jquery-ui-selectable
The jQuery UI Selectable plugin: Enable a DOM element (or group of elements) to be selectable. Draw a box with your cursor to select items. Hold down the Ctrl key to make multiple non-adjacent selections.
The jQuery-ui Selectable plugin allows for elements to be selected by dragging a box (sometimes called a lasso) with the mouse over the elements. Also, elements can be selected by click or drag while holding the Ctrl/Meta key, allowing for multiple (non-contiguous) selections.