The above answers are correct. However, in the context of internet surfing, the difference will be: Tags (also referred to as custom tags) are information that users can enter to their individual posts that helps in creating a taxonomy for other users when searching for something. Labels are a different type of method to create meta-categories for topics as a whole and are configured by the original author of a topic or TKB article only. This can be used to help users that are browsing the community looking for posts on a specific overarching topic :-)

Here's one difference: A tag is always a separate piece of paper/card/plastic which it attached to a product, often by means of a string or tie of some sort. You can generally pull or cut it off quite easily. Tags usually have prices on them. It is possible, but less usual, to use 'label' in this case. A label is often more permanent, and has the name of the product on it - think of a label on a bottle of wine, for example. A label on a bottle, jar or can is stuck to the product by means of glue, and you would not normally remove this. In clothing, the label is sewn into the garment (usually at the back of the neck), and you wouldn't normally remove this, either.

A tag is usually attached to the item or person in a manner that it will hang off. Example: A price tag hangs off the sweater sleeve. A label will go over the item and it is usually completely attached. Think of a food label, the words are stuck on the item. They are not hanging off.