Google was lacking any sort of enforcement for bending or even breaking their Webmaster Guidelines, and only had time to punish the most egregious of offenders.
Link spamming is stands for black hat search engine optimization. There are few method which are mentioned spam in google's list.
Directory submission
Bookmarking submission
Single Article submission on multiple sites
footer links
keyword specific sidebar textlinks
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 backlink from other sites. So keep in mind all those feature and take backlinks from high authority and different IP address. There are few methods you can read when you create baclink for your website.
Get Quality Backlink to Your Blog in 2016 - Computer Geek Blog
Also do guest blogging for your brand and you can find list of guest blogging sites
List of Quality Guest Blogging sites for 2016 - Computergeekblog
Spam indexing is the act of web index spamming. It is a type of Search Engine Optimization (SEO) spamming, which is the specialty of making a site alluring to the real web indexes for ideal ordering. ... Spam indexing is in some cases used to attempt and control a web crawler's comprehension of a classification.
Search Engine Spamming is the practice of deliberately and dishonestly modifying HTML pages to increase the chance of them being placed close to the beginning of search engine results, or to influence the category to which the page is assigned in a dishonest manner.
In computing, spamdexing (also known as search engine spam, search engine poisoning, black-hat SEO, search spam or web spam) is the deliberate manipulation of search engine indexes. ... Search engines use a variety of algorithms to determine relevancy ranking.
spamdexing (also known as search engine spam, search engine poisoning, black-hat SEO, search spam or web spam) is the deliberate manipulation of search engine indexes. ... Search engines use a variety of algorithms to determine relevancy ranking.