Medicos often talk of Occult blood which simply means blood which cannot be seen with the eye. However, the word has undergone a change of meaning in that narrow sense to now encompass a whole area of beliefs outside the mainstream of all World Religions.
People see the occult in different ways.
Some conservative Christians see anything that is not 'Christian' as being 'Satanic' and thus part of the Occult. On the other hand those involved in the occult see it as spiritual, mysterious, and a source of knowledge and healing power. For example, a shaman performing a healing spell might believe that the spell taps into absolutely natural forces. They find it difficult to comprehend the Christians position that they are part of the Occult because they do not believe they are dealing with anything supernatural. On the opposite note, some conservative Christians have gone so far as to regard all music that is not sung in church as being of the devil - therefore occult.