Tags are used to identify the object, however the main purpose of tagging is grouping objects that have similar or identical attributes. This process is needed to better sort the large amount of items. Sometimes numerical or hierarchical identification is impractical or inapplicable, therefore a certain specification is chosen as a determining factor. This word or attribute is then used to group items that share this characteristic. Some tags may contain warning messages that display hazardous attributes or possible behaviour of an object, serving as a sign. Blank tags may have informational headers or be completely empty with designated space for the description.