what is meaning of spam link?

Link form low quality website are called as spammy links

Link spam is also known as comment spam, blog spam or wikispam. Link spammers usually don't leave comments of any value along with their links. The purpose of link spam is to increase the number of external links made to a site the spammer wishes to promote.

Hi Friends,
Basically when you submit dozen of directory and bookmarking links, you haven't checked IP address. Most of all bookmarking and directory list that you get for submission  hosted on same IP. And you are getting many repeated links from Same IP address that is called spamming.

Google read authority, IP, relevancy when you create back link from other sites. So keep in mind all those feature and take back links from high authority and different IP address.  There are few methods you can read when you create back link for your website.

Link spam is the posting of out-of-context links on websites, discussion forums, blog comments, guestbooks or any other online venue that displays user comments. Link spam is also known as comment spam, blog spam or wikispam. Link spammers usually don't leave comments of any value along with their links.

links from low quality sites are known as spammy links

Link Spam is basically content on the web that is created solely for the purpose of building links. Different people will give you different opinions to what exactly they consider to be link spam.