Sawaab e Jariyah means ongoing Sawaab. An example, a person who digs (or causes to be dug) a well from which people can draw water, free, with the intention of doing it for the sake of Allah.  This is an act of charity which continues over time, and as long as people benefit from the well, the donor, dead or alive, will continue to receive credit for having done it.

Teaching can also be an ongoing sadaqah. Suppose a person teaches another to recite a verse of the Qur’an, or how to take care of a baby, or how to take out an appendix. As long as the knowledge is used, the teacher continues to reap credit for it.

Gunah e Jariyah: means ongoing gunah. e.g if a person teaches some one to rob , so whenever a person robs the teacher will also get gunah for his wrong teachings.

Another example, if a person brings TV or music system at home, so whenever his family sees movies or listen to music, song and dance and al faahisha, the person who brought this at home will get gunaah for sin even after his death..

So, make sure your actions earns you sawaab e jariya and not gunah e jariya.