Remember back in the day before Google made is big as they are today? When I was first told about google.. I think it was like 98 or 99, someone sent me over there to check the site out.. They were like, man you have to check this site out, it doesn't have ads anywhere around it or anything & it gets you what your want most of the time at the very top of the list. If you remember back to them days, the most popular alternatives was yahoo, atavist and lycos. They were all COVERED with ads. You had to go pages & pages to find what you wanted. Google, on the other hand. No ads & everything was on the first page! So at this point, there was also a small message on google.com that mentioned welcome to their search engine, they're not going to be spammy and evil like all the other search engines out there but they weren't sure how they were going to make money yet.... So, they eventually came out with small text ads. There wasn't many of theme other, just a small amount barely noticeable on the right side of the page.. Boy has all that changed. What started it? Well guys, I have to say it is Internet Marketing unfortunately. People that caught onto exactly how the whole algorithm worked, realizing that to make their page get higher they needed more links back to their site. So people started spreading out link backs that weren't very relevant, paying others to link in, etc. While it does help for people who want to make their site visible, it makes the sites that honestly more relevant disappear... Thus Google's searches is now pretty much exactly like yahoo's was back then. If someone invested enough money they could get their page to go up higher on the list, a better place in the directory etc. Now Panda was meant to change this, however that was a bad idea. Why? Well, google had fostered this internet community, a conglomerate of people that could actually make a living off of the model they had developed. Thus, ripped the rug out from underneath everyone that have become accustom to this world was in fact EVIL. Google has established itself as #1, while many of their searches showed affiliate marketing like no other, you couldn't get to what was really relevant.. Many of the sites out there, actually sold products directly, and the new system ruined that as well because even the big guys used the same SEO tactics knowing that is the way to be recognized. In the end, Google from what is sought out to be at the beginning is nowhere near that today. They are evil, they are a conglomerate, and nothing is relevant anymore than the other search engines these days.
We generally get irrelevant search results in Google because some people goes with keyword optimization without relevant information (keyword stuffing). Google have implemented a system called a "quality Score" in relation to the keywords you use, the ad you write and most importantly the landing page the ad points to. Here, good quality catches Google's search positions.