SEM or Search Engine Marketing is very much like SEO but more beneficial to google as a whole and more accepted by it. Unlike SEO which pushes a site up with merely putting keywords to push a site up.
In SEM, The Advertiser bids on a Keyword and from there they get preferential treatment by google whenever someone searches that exact keyword as their site is right up the top as featured.
This is much more reliable, faster and aggressive way to make yourself known and costs much more than what SEO can in terms of money spent.
SEARCH ENGINE MARKETING
If you have money to spend on advertising, SEM is not a bad option.