"The lazy teacher is watching television."
Translation:게으른 선생님은 텔레비전을 보고 있어요.
Adding -고 있어요 to the verb stem allows to approximate the English present continous. The so called -ing form in English.
보 is the root of 보다 (to see/to watch). When making it a continuous verb (watch-ing), drop 다, add 고, and then add the proper ending to complete the sentence. The way I've understood it so far, ~고 is sort of equivalent to the English ~ing.
Please, someone correct me if I am wrong.