Omega-6 is a group of essential fatty acids (EFA) that our bodies need.
Linoleic acid is an Omega-6.
Dietary sources of Omega-6 fatty acids include vegetable oils such as corn oil and soy oil -- they contain a high proportion of linoleic acid. Omega-6 acids also come from cereals, whole-grain breads, eggs and poultry, etc.
(Note that Omega-3 fatty acids are the "really good" ones we often don't get enough of. Many people have taken to eating more fish or taking fish oil supplements to get more Omega-3s in their diet.)