In lay mans terms, what is the difference between online SEO and offline SEO services?

We are hunting a company to provide SEO services. They asked us whether we need online or offline SEO services. Can anyone please provide what these mean in laymans language?

For a sports based social network, what is essential of the two?

I think you mean "On-Page" SEO and "Off-Page" SEO.

On-Page SEO : On-Page SEO are things that you can do ON a HTML page to tell Google and other search engines about your page. So for example, selecting the right keywords that are relevant to the page's content and using them in the title, optimizing your header tags (h1/h2), the alt-text in images and the meta title and description etc,. are some On-Page SEO techniques.

Off-Page SEO : Off-Page SEO involves things that you do OUTSIDE your page and get more inbound links to your page from other reputable websites. After creating great content in your page, you can submit your site to Directories, start a conversation with sites linking to your competitors and get them to link to you etc,. These are some Off-Page SEO tactics.

For a given page, On-Page SEO is about 25% important and Off-Page SEO is 75% important. On Page SEO is completely under your control, but Off-Page SEO is not. Off-Page SEO takes time and is very effective.

You can find more information at http://help.hubspot.com/articles/Methodology/how-to-optimize-your-content and http://blog.hubspot.com/blog/tabid/6307/bid/6487/The-ABCs-of-Off-Page-SEO-Tactics.aspx A final word of caution: If you do sign up for off-page SEO services, make sure you dont get scammed.

The On-Page SEO covers what is done on the pages of the website and Off- Page SEO covers activity that takes place elsewhere i.e link building.

The On-Page SEO services are:-
Meta Description Tags
H1 Tags
Alt Tags
URL structure
Internal Link Strategy
Content

The Off-Page SEO services are:-
Forum Posting
Blog Commenting
Onsite Blog Posting
Local Listing
Social Media Activites