In order to understand the three basic concepts in terminology (object, concept and term) let us use as example the term "hammer".
The concept of "hammer", represented by the term and also by the sign "hammer", does not refer to a specific hammer, but more to a general idea, perception or understanding of all objects that have certain characteristics in common - such as being "a handtool consisting of a handle with a head of metal or other heavy rigid material" commonly used for striking or pounding - and therefore can be classified under the concept "hammer". The object hammer is the item as it is.