welcome to the forum. we all were once a newbie so its ok your safe. no bashing in this forum, we are to help.
tag could mean different things, depending on what you are trying to do. is it pictures? or facebook?
Welcome!! A "tag" is a key word(s) for the topic of your thread - to help others find the thread when they search for the same topic.
We were all new once. Just jump in, start reading, and get involved - you'll catch on in no time. Don't hesitate to ask questions, and join in the fun!