Google and Themes
In general a theme may be anything, like it could be some matter or could be any color, however regarding Google, a theme is the topic that reflects the Website page. Like if we talk about a jewelry site, the theme of site would be based on jewelry.
All good search engines, like themes to the extent that they influence a page's rankings and so does Google. Generally lot of people worry about the page rank, they always try to achieve higher page rank then the previous one.
It’s not a dream that a small sit or a new website can achieve high rank, it is actually possible, how? It is possible if and only if your site is all about of one theme. Sometimes some sites consist of other themes which reduce their PageRank .
Another example supposes my website theme is jewelry and I include all the ornaments in my website like, ring, bracelet, necklace, beads etc. However there is another website, has only bracelet theme, that time there is great opportunity to that website for getting higher rank as compare to my site, because that website completely has a single theme.
One more thing is linking the page, generally we do prefer to link the page with the product for example if we want to link product, bracelet then we have to link it from bracelet page. By doing so, we exactly build up the page rank of our website.