Obviously we need to say a word or two about SEO software. Whether it is safe using it, whether it is worth to purchase some and other matter. Since we have two types of SEO activity - on-page and off-page - all the software can be categorized the same way. However, I would prefer another classification:
- Keyword tools
This includes tools that perform some keyword research, whether on the Web or by means of analysis of some website. Such tool can gather or try to calculate the popularity of a keyword, some of the artificial keyword parameters (like the keyword density), suggest some synonyms and other keyword related stuff.
- Web ranking SEO software
This is simply tools that check the position of your site in a search engine. This refer to the above section on the web ranking checks.
- Link tools
Link building, managing, structurizing, buying and selling software.
- Submission tools
This bunch of different SEO tools try to submit your website or some particular pages to some web resources, like web directories, catalogs, search engines, article sites and others.
- All-in-one packages
A swiss knife performing all the tasks. A big fat SEO application having all (or nearly all) needed (and sometimes unneeded too) functions within.
- Automation SEO software
In this category I don't mean the automated software. Actually, all of the above kind of tools are working more or less automatically. However, there are some tasks that cannot be fully automated and thus still need a human intervention. This includes managing your AdWords or AdSense accounts, finding link partners, tracking some interesting blogs etc. So such SEO software simply helps you to fulfil those tasks, still requiring you to do the most of the work yourself.
All of the above can be a software tool working on your computer, or a online tool working remotely through a browser.