Search engine optimization, or SEO, is the practice of optimizing a website in order to improve its ranking in search engine results pages (SERPs) and increase the amount of organic traffic that it receives. It is an important aspect of online marketing because it helps to ensure that a website is visible to the right people at the right time.

There are several reasons why SEO is important for online marketing:

1. Increased visibility: One of the main benefits of SEO is that it helps to increase the visibility of a website in search engine results pages. This is especially important for small businesses, as it allows them to compete with larger, more established companies by making it easier for potential customers to find their website.
2. Higher conversion rates: Websites that rank highly in search engine results pages are more likely to be visited by users, which can lead to increased conversions. This is because users are more likely to trust websites that appear at the top of the SERPs, and are therefore more likely to make a purchase or take some other desired action.
3. Cost effectiveness: SEO is often more cost effective than traditional forms of advertising, such as pay-per-click (PPC) advertising. This is because the traffic that is generated from organic search results is free, whereas traffic from PPC ads must be paid for.
4. Long-term results: SEO efforts can have long-lasting effects, as the improvements made to a website’s ranking and visibility will remain in place as long as the website continues to meet the needs of search engines and users. This is in contrast to paid advertising, which stops generating traffic as soon as the advertising budget is exhausted.

Overall, SEO is an important aspect of online marketing because it helps to increase the visibility and credibility of a website, and can generate long-term results at a lower cost than traditional forms of advertising.