It vs This, that etc
I don`t understand when I can use 'it' and when I can use 'this'.
I watched Madagascar and King Julien tell lemurs: 'keep Mort out. It`s so annoying'.
What did Julien mean 'Mort is so annoying (He is annoying)' or 'This is so annoying'?
I just don`t know how say better. 'This will be cool' or 'It will be cool' when I mean a event will be cool.