Electric field lines are the way to visualization of electric fields.
Electric field is a region around a charged particle or charged object in which a force would be exerted on other charged particle or charged object.
Electric field lines begin at a positive charge and end at a negative charge. In the absence of a negative charge, electric field lines end at infinity. And in the absence of positive charge, electric field lines start at infinity.
The number of electric field lines is directly proportional to the magnitude of charge.