Search engine optimisation (SEO) is the process of optimising your website for search engines in two ways. The first way is making sure that search engines know what your website is about and therefore, can rank it for relevant searches. The second way is increasing the online authority and trust of your website, so that search engines see it as deserving to rank ahead of your competitors.
Technically, you don’t directly "pay" for SEO, it's an earned media channel. But Google uses more than 200 factors in its ranking algorithm, so to do SEO well takes an investment in time and expertise, so it’s worth working with an expert where you can.
Search Engine Marketing (SEM) is a little harder to define because many disagree on it's definition. However, Wikipedia states:
"Search engine marketing (SEM) is a form of Internet marketing that involves the promotion of websites by increasing their visibility in search engine results pages (SERPs) primarily through paid advertising. It may also incorporate SEO"
So let's stick with that. SEM is a collective term to describe SEO and paid search advertising (like Google Adwords) together.
If you’d like to find out more about online marketing and how it could help your business, please feel free to get in touch – we’d love to help!