An electric field is a vector quantity and can be visualised as arrows going toward or away from charges. The lines are defined as pointing radially outward, away from a positive charge, or radially inward, toward a negative charge.
The lines represent the lines of force and are often called the electric field lines. They are typically drawn as a pattern of several lines extending from the charge.
The electric field lines point in the direction that a positive charge would accelerate if it were placed upon the line. This means that the lines are directed away from positively charged source charges and toward negatively charged source charges. To indicate these directions the electric field lines include an arrowhead that points in the appropriate direction.
In theory the pattern for an electric field would consist of an infinite number of lines. In practice, this would make any diagram unreadable, so in the interest of clarity the number of lines is usually limited. Normally just a few lines around a charge to indicate the electric field is sufficient to show the nature of the electric field in the space around the charge.