PPC isn't a part of SEO, but rather a whole separate thing. PPC is great if you need traffic (and don't forget - conversions!) fast. But, if you don't have a large budget and time is on your side (and you're also not in a very competitive field), SEO usually produces a better return on investment in the long run.
To be clear for any beginners - seo stands for search engine optimization. This concept refers to the practice of optimizing text and other factors on a Website (and off of a Website, primarily building links to the site from other sites) so that it ranks higher in search engine results for targeted keyword searches.
PPC stands for pay-per-click. This concept refers to a bidding system that allows advertisers to post ads that appear when searches related to keywords selected by the advertiser are made. The advertiser is only charged when the ad is actually clicked, and is not charged just because an ad is viewed.
SEO generally takes more time than money; conversely, PPC takes more money than time (though some time must be spent in the initial stages for research, build-out, etc.)!