Plz, Explain off and on page optimization in search engines.

On-page optimisation means optimising the title,description,keywords and heading tags(if any) for your targeted keyword/keywords. While doing on-page optimisation ..be sure not to stuff the keywords because it may lead to spam.
Off-page optimisation means link building for your sites. This can be one-way, two-way or three way. Now a days, Google prefer one-way links exchange. But in case of new sites it's merely impossible to get a one-way links exchange. So, if your sites is a new one you can go for two way links exchange first.
To get a listing in a search engine both on-page and off-page optimisation is needed