Natural selection is the idea that the creatures more suited to an environment will live long enough to reproduce and pass on their genes. So in an example, birds with genes that code for long thin beaks may live longer because the size of their beaks allows them to probe into small spaces for insects, allowing them to feed easily, and so live longer. They can reproduce and their genes that code for a longer beak are passed on. The ones with shorter beaks have less chance of competing for food because they cannot reach hard to reach places so have less food available so die out more. Other creatures may flourish with more strength, or better eyesight etc. Similarly, bacteria with genes that enable them to withstand e.g. heat allow these bacteria to set up colonies in hot springs, where other bacteria would die out. Natural selection does not cause genetic information, as reproduction (in whatever way - sexual, binary fission etc) produces genetic information. So basically natural selection is the result of genetic information. Genetic mutations arise in the wild that may or may not give creatures an advantage over others of the same species and so coupled with exchange of genetic material e.g. during sex, leads to constantly genetically new creatures being born.

i'd say natural selection is a result of genes, picking out the weaker genes, and letting stronger genes survive.