Eren Yeager was a former member of the Survey Corps. He was the main protagonist of Attack on Titan. He lived in Shiganshina District with his parents until the fall of Wall Maria, where he impotently witnessed his mother being eaten by a Titan. This event would lead to Eren's intense hatred towards the Titans as he swore to wipe all of them off the face of the Earth.
Soon afterward, his father, Grisha Yeager, found him and gave him the key to his basement, instructing Eren to find it at all costs and retake Wall Maria. He then injected Eren with a Titan serum.
Eren was a young man of average height and muscular build. His facial features strongly resembled his mother's; he had a reasonably long, rounded face and sizable, expressive, gray eyes. His hair was short and black, and his bangs fell in a natural, middle-parted, curtain-type style. After his training and during his time as a soldier, he became very physically fit and muscular, although this was often unseen due to his relatively baggy clothing. After the four-year time skip, Eren grew his hair down to his neck.
Appearance: Eren was a young man of average height and muscular build. His facial features strongly resembled his mother's; he had a reasonably long, rounded face and sizable, expressive, gray eyes.
Personality: Eren was best described as hardheaded, strong-willed, passionate, and impulsive, which are attributes of both his strong determination to protect mankind and, eventually, his equally strong determination to escape the Walls. Even as a young child, he was so intent on joining the Survey Corps that he argued with and shouted at his mother, referring to the people in the village as "silly" and comparing them to complacent livestock.
History: Eren was born in Shiganshina District on March 30th, 835, in the southern region of Wall Maria to Carla Yeager and Grisha Yeager. During his childhood he encountered a crying Armin Arlert, and questioned why he never fought back against the neighborhood bullies, after hearing the boy's reasoning of refusing to run, he formed a friendship with him, and went on to defend from bullies.
Eren Yeager in the story: After Eren is woken from a nightmare by Mikasa, the two walk home through Shiganshina. They are greeted by Hannes, who begins teasing Eren for having apparently cried in his sleep. Eren is annoyed to see that Hannes and his friends are slacking off on the job and refuses to be placated by their claims that the Titans will never breach Wall Maria.
Source: Attack on Titan Wiki, available under CC BY-SA 3.0.