Gerunds, or sometimes called verbal nouns, is a verb which end with "ing". Yes, that is it. The only point you have to concern about gerund is that when the verb is ended with "ing" they could be either gerund or present continuous. You need to know when it is gerund or present continuous.
Difference between Gerund and Present continuous.
1. When the V + ing acts like noun, it is a gerund.
-- Walking everyday is a very good excercise.
-- I went to the sightseeing with my family last week.
2. When the V + ing acts like verb. it is a present continuous.
-- John is walking
-- Don't go away. I am talking to you now.