One is the traditional, ever increasing counter script. The other is averages the number of hits you receive over time and reports number of hits per day. This document explains how to use the counters in your own web pages. It can be useful to determine which pages are more popular and to give you that nice rush when it jumps to two digits. You should first have an already established home page.
Counters are much more useful on completed pages.
It's not considered overly useful to place a counter on a page that just says 'under construction'. Choose a unique identifier. Next, choose an identifier that will uniquely name your counter image. If you have just one counter, we recommend your username as the identifier. Place the inlined counter image in your page.