Table of Contents

SEO or SEM Banner for web development

What do they stand for?

SEO = Search Engine Optimisation

SEM = Search Engine Marketing

*Another related term that will be heavily mentioned throughout this article is SERP (Search Engine Result Pages).


How does it work?

Before we learn the difference between SEO and SEM, let us dive into how Search Engine works in order to better understand things. The 3 main factors about Search Engines are:


  • Algorithms

Search Engines such as Google have their own algorithms. Little is known about how the algorithms are calculated and Google has never publicly stated which algorithms it uses. Therefore, people are not able to beat the system by filling their site or pages irresponsibly to raise their ranking on the SERPs. The algorithms are regularly reviewed and refined to prevent any new methods that are used to cheat the system.

To quote an example, at one point it was discovered that one of the factors of Google’s algorithms was to repeat keywords in a blog. This caused many bloggers to spam the keywords in white, in-between paragraph spacings. The keywords were detected by bots but not seen by the reader. This resulted in many blogs ranking high not because the contents were useful but because the keyword was repeatedly mentioned.


Photo taken from SiteChecker. Click here to read the list of updates in-depth.


  • Crawlers

Knowing the algorithm would be useless without bots known as “Crawlers”. Crawlers are a type of program that visits every site and pages thoroughly. For example, Google’s crawlers are known as “Google Crawlers”. It records the entire page’s contents and saves them to the search engine provider’s storage. These crawlers not only record the site’s data but also scan through the contents and use the algorithms as checklists to rate the site.

Crawlers are constantly evolving and repeatedly upgrading. A simple crawler that just visits and records sites has since been supported with features such as the ability to detect sites using white texts to raise SEO.

What is a Web Crawler?

Picture taken from Search Engine Land.


  • Index & Indexing

With the algorithms as a checklist and the crawlers as bots to explore and retrieve site data, you might ask what is index or indexing. Indexing is a process in which the data brought back by the crawlers are stored in a database. Index is the database where the recorded data are sorted into their ranking according to their SEO and other factors.

In simple terms,

  • Indexing is the retrieving and recording of site data by crawlers.
  • Index is the records of the data collected and sorted.

seo crawler web development step

Image taken from The Next Scoop. Click here to read more about how indexing works in-depth.


  • Search Engine Result Page (SERPs)

This is where the difference between SEO and SEM is much more obvious. The crawlers visit and rate sites based on their SEO-friendliness according to their engine’s algorithms. Depending on the rating, the sites are listed on SERPS according to their ranking. The results listed are based on the page’s SEO-relevance.

Example of SEO & SEM results in web development

Example of a SERP with SEO & SEM results. (Green = SEO-based. Red = SEM-based.)


SEM-based results, on the other hand, can be found mostly at the top or the bottom of SERPs. These results are easily identified by the tag that shows “Ads” or “Sponsored”. This is because unlike SEO which is content-based, SEM results are paid to be exclusively displayed.


I’ll just pay my way through then!

Some of you may consider just paying search engines to display your results. However, the ranking of SEO applies to SEM ranking as well. Even if your site has paid to be displayed, it might not be the first SEM result to show if your site’s SEO lags behind others. It is not mutually exclusive and both have to be monitored.


How do I improve SEO then?

With the knowledge that SEO is a must regardless of whether you opt for SEM, there are 2 parts of SEO you’ll need to know – On-site and Off-site SEO. Both are equally important in boosting your rankings.

  • On-Site

For on-site SEO, there are rules you can implement on your site to make it more search engine-friendly. For example, having a clear title, well-written description, well-formatted URL and many more.

  • Off-Site

Off-site SEO refers to getting votes of other sites to gain the trust of search engines. To garner votes, your site should be linked on other sites. For every site that links either a keyword or suggestion to your article or such, it gains a vote. It also includes linking your own site’s pages with each other to build a strong foundation. Do note that linking alone does not prove to be effective.

on and off-site SEO factors in web development

A list of SEO factors to consider. (Left = Key Phrases. Right = Readability.)


Some factors to consider in your content would be the ones you see below. Things such as keyphrases, image attribution or even titles are important. Readability is also important. After all, a bulky site with tons of content that isn’t readable is not very useful.


Any extra tips, advice or such?

If you are interested in learning more about SEO, head over to Yoast. They provide free SEO educational courses as well as SEO packages that can assist your SEO improvement. They also offer SEO plugins for wordpress which helps to rate your contents.

You could also consider looking at our SEO solutions. Don’t forget to check out our other posts to learn even more!