Pagerank 0 what does it mean

I entered my URL into Dp pagerank tool.

It said the position was number 1.

but what does this mean, i do software and apps, but im sure im not number 1 on google for those keyword.

 

It just means your site is a Pagerank 1
0 is the lowest and 10 is the highest, it has nothing to do with being No1 in Google, it's just a meaningless metric and not worth worrying about.
https://www.google.com/search?btnG=1&pws=0&q=what+is+pagerank

 

Also, remember the Page rank is the rank of the specific page...not your whole site. Each page of your site will have different Page Ranks