Semiotics is the study of signs. With semiotics we have denotations and connotations. A denotation is what we see when we look at an image - simply what it is. A connotation is what we understand from this image, so what the image could mean.
This poster is for hit TV show Glee. Straight away we see a couple (Rachel and Finn). This is a denotation. The couple are larger than most of the other characters and in the centre of the poster. From this we can tell that the main storyline revolves around these two characters. This is a connotation. We can tell that they're in love as they are staring into each other's eyes; Rachel has her hand on Finn's leg; he has his hand on her face; his mouth is open in a way that suggests he is singing to her.
On the right we see one of the biggest characters (Coach Sylvester) on the poster. The fact that she is bigger than the rest suggests she holds power over them. We see that she is the 'villain' as she is pulling the plug - literally - on their show, causing the 'e' in 'Glee' to blow out and smoke. This suggests her storyline - she tries to stop the Glee club throughout the show. The fact that she is in uniform and is blonde makes the audience think back to Nazi times - she is almost a dictator.
To the left we see the other biggest character on the poster (Mr Shue). He is dressed like a typical teacher, and the fact that he is smiling and leaning back with his hands in his pockets suggests that he is the laid-back, cool teacher - the exact opposite to Coach Sylvester. Typically enemies stand on opposite sides of the image, which suggests that they have conflict throughout the show.
At the back of the poster is a girl, Quinn, higher than the rest, suggesting she believes she is higher in society, almost like a 'queen bee'. She is also in uniform, just like Coach Sylvester, showing that she is a follower of the villain and therefore enemy to the rest of the characters.
Sitting on the 'G' of 'Glee' is another woman (Miss Pillsbury), presumably another teacher due to her formal attire, staring at Mr Shue with her hands over her heart. Her entire body is turned towards him showing that she can't help herself, and there is a look of desire on her face. This automatically gives away the main storyline of her character - she is irrevocably in love with Mr Shue.
The other four characters on the poster are members of the club - we can see that they are united in some way as they all, along with Finn and Rachel, are dressed in shades of blue. Each are very different - there is a male in a wheelchair (Artie), a clearly homosexual male (Kurt), an Asian goth (Tina) and an African-American female (Mercedes). Each have clear storylines that we can see just from the poster.