It’s one of those questions that isn’t easy to answer, but here’s my advice…
Speaking the same language
Let’s make sure when we say “traffic” we’re talking about the same thing.
First, there are a lot of stats and metrics involved with traffic. Examples: unique visitors, visits, hits (although “hits” is such a vague, unhelpful term in my opinion). They all measure and indicate different things.
Second, you have to specify a time period for which you are measuring traffic. I’ve heard statements like, “Her site has over 1 million visitors!” Alright, but are you saying she has over 1 million visitors per month or are you saying she’s had over 1 million visitors since she began her site 5 years ago?
For the sake of example, let’s talk pageviews
For many years, especially in the days of display ads, “pageviews” was used when conversing about traffic in general. Unique visitors or unique visits are stats that are talked about more these days, but for the sake of this example let’s concentrate on page views.
A page view is counted each time your site loads.
For example, when someone lands on your main page and your site appears on the screen, that’s one pageview, because your site loaded. The visitor might scroll down to read (still the same pageview) and then click over to another one of your posts. When they click, your site will load that new post (on a new page) and that will be a second pageview. And so on.
In general, when bloggers talk about traffic in page views, the default is monthly page views (as opposed to daily or weekly or yearly).