Internet marketing is a very common work but till very effective and valuable skill for the marketers. There are SEO, PTC, Blog Posting and other methods of internet marketing. For example I am working with fastmoneyearning,com so I can find some keywords based on my website and make SEO article. Also backlinking would help in marketing the website. Special terms like the website above is paying $1 per click can attract more viewers.

No advertising, there are many sincere ways you can advertise in Cokoye such as listing in www.Cokoye.com/yellowpages   or pay for advert see rates here http://cokoye.com/general-chats-room-forums/cokoye-advert-rate-how-to-advertise-in-cokoye
See Cokoye free forum marketing see guide here  http://cokoye.com/internet-marketing-discussions/cokoye-step-by-step-forum-marketing-guide

How do you call this advertisement except a suggestion for people who visits this page? Can you explain me the concept of advertisement and suggestion post.

I don't know what you mean or want again, if you're an online marketer there are decent ways you attract users or customers to your business/website (which I listed to you) using forum like Cokoye other than the way and manner you spam the forum by posting virtually same content every where.

When I've started my career as a freelancer I have always looked for a solution that can give me some extra money. There were nothing that could help me. If I suggest something that you consider spam can you help me telling which are not spam. Because I am not sure how forums deal with spams.

Thanks in Advance.

See Cokoye free forum marketing see guide here  http://cokoye.com/internet-marketing-discussions/cokoye-step-by-step-forum-marketing-guide
With above you will be fine. You don't go around posting and talking about your website or business people don't visit forum for that. But cokoye tries it best by identifying that your type exist in forum hence creating above sections for you.
Example of how forum works see how discussion below are going and that will tell you why people visit forum:

How to know if woman is interested or just being nice
http://cokoye.com/love-relationship-romance-chat-room/how-to-know-if-a-woman-is-interested-or-just-being-nice/

What are you listening or have listened today?
http://cokoye.com/musics-discussion-forum/what-are-you-listening-or-have-listened-to-today/

What is your favorite color
http://cokoye.com/general-chats-room-forums/what-is-your-favorite-color/

About to weed his wife, girl friend call that she is pregnant
http://cokoye.com/love-stories-forum/about-to-weed-his-wife-girl-friend-call-that-she-is-pregnant/

Long distance relationship does it work?
http://cokoye.com/love-relationship-romance-chat-room/long-distance-relationship-does-it-work/

What is the Genesis of Wearing of Trousers Dropping Beneath The Waist?
http://cokoye.com/family-and-home-discussion-forum/what-is-the-genesis-of-wearing-of-trousers-dropping-beneath-the-waist/

How many partners have you had?
http://cokoye.com/love-relationship-romance-chat-room/how-many-partners-have-you-had/

What book are you currently reading?
http://cokoye.com/literature-and-books-discussion-forum/what-book-are-you-currently-reading/

Why are you in Cokoye?
http://cokoye.com/hi/why-are-you-here/

If love hurts, is it still love?
http://cokoye.com/love-relationship-romance-chat-room/if-love-hurts-is-it-still-love/

Africa's problem spiritual or intellectual
http://cokoye.com/society-discussions-forums/africa-as-developing-continent-spiritual-or-intellectual-problem/

In Africa infidelity is taken lightly why?
http://cokoye.com/love-relationship-romance-chat-room/in-africa-men-infidelity-are-taken-lightly-why/

Scary pictures (for fun)
http://cokoye.com/entertainments-discussions-forums/post-the-most-scariest-photos-here/

Ugly pictures (for fun)
http://cokoye.com/entertainments-discussions-forums/ugly-pictures-do-you-have-ugly-pictures-uglier-than-these-pictures/

Funny pictures (for fun)
http://cokoye.com/entertainments-discussions-forums/let-share-funny-pictures/

What is your superstitious belief?
http://cokoye.com/society-discussions-forums/what-is-your-superstitious-belief/

What is the best thing that happens to you today?
http://cokoye.com/general-chats-room-forums/what-was-the-best-thing-that-happened-to-you-today/

Why do so many marriage fail?
http://cokoye.com/family-and-home-discussion-forum/why-do-so-many-marriages-fail/

Tips to promote or market your business, band, service or idea in Cokoye
http://cokoye.com/internet-marketing-discussions/cokoye-step-by-step-forum-marketing-guide

You can start topic of any kind as Cokoye is general forum or joining thousands discussions going on.