whats the diffrence between no follow and do follow

i really dont understand whats the diffrence between these 2, for example if i have 100 backlinks that are no follow ,does this mean that search engines dont count these links?

 

Google does not count them as links at all. Yahoo does. I'm not sure about the other SEs.

 

Focus on getting DoFollow links. They will help to improve your SERP and PR.
NoFollow links (like those from blog commenting and some social bookmarking sites) are good for direct traffic only.

 

Dofollow is telling Google to follow the link, index it and pass PR from the site giving the link to the receiving site.
Nofollow tells Google to follow the link but not to give it any link juice.
So from a link building point of view its best to get dofollow links, but nofollow links can also be good if they are on a high traffic site, for example Yahoo answers nofollow all their links but its good for a bit of traffic.

 

Both are useful depending on what you are looking for. The above posters have explained the difference but this article about Building Back Links for Your Website may help understand building links better.

 

thanks for the info, now everything is clear to me

 

Google does not count nofollow links.... Yahoo does count nofollow and dofollow links...

For a more indepth breakdown, please read this:
What is DoFollow? What is NoFollow? Follow Along and See.