In SEO, a category page is similar to an index on your website. On an ebusiness site which sells dog food it is the page that itemizes the types of dog food for sale. On a service site it would be the list of all your services and on a niche SEO information website the category page would possibly itemize SEM/SEO articles.
Category pages are more SEO keyword and keyword phrase rich than your homepage, as a rule. If there is a big competition for your homepage keywords then, as a rule, your category page should include more precise keywords. Also the keywords on your category page will more likely be acceptable. Websites which have only one homepage can embody any amount of category pages and this may increase their traffic. This should please any SEM/SEO analyst as it is their goal to grow your customer base.
There can also be varying stratums of category pages. For instance the first tier page could be Dog food then Adult Dog food and then the final tier could be Vegetarian Adult Dog food. If your website is set up with more than one category level you must fix on the ones on which you wish to spotlight. Sometimes not all the same things can be done on each category level and sometimes they can. Your search engine optimization (SEO) plan should focus on what you want to accomplish most.
Category page SEO will be much easier since most of the links will be internal therefore, coming from different places in your own website. You should use SEO keywords to anchor your text when you link to the category pages. They should stand out when placed in the headings and title tags on the page. It is also helpful for you to write some content that is SEO keyword rich. A paragraph, maybe two, should be plenty. Remember you want your page keyword rich not keyword stuffed, which is a no-no in proper search engine optimization.
Your internal linking is highly important for your SEO. You must be sure that for every level of category page, you have a link on your homepage site map which corresponds to it. It helps to link to the categories from all the pages in your website, though in order to keep your menu small and to have less links only put the main categories. Leave the subcategories to be listed on the category page itself. This will avoid having too many links which can bring down the weight of each link. Search engine optimization (SEO) is a delicate balance between too little and too much so ask a SEM/SEO expert for help.