Anime are productions of hand-drawn characters and animation. Actually, most anime first originates from manga. Manga is the comic book version of the series, and it is often the original version of the storyline. Manga, however, cannot feature the effects of fast paced actions done by the character, for example, Luffy’s punches in One Piece. Hence, anime was created to bring manga to life, and give these characters a chance show their lives in motion with voices and sound effects.
Here's a picture of Luffy punching Ceaser in the Manga comics compared to the Anime:
Here's a picture of Luffy punching Ceaser in the Manga comics compared to the Anime:
Here's another comparison of a Nisekoi scene between the Manga comics compared to the Anime: