In the US, a lamp post is a kind of street light that is found in the old sections of old cities. They're not common.

Thank you so much :)

I think lamp posts are a remnant when they actually put candles up there a couple hundred years ago. Like a couple other users have mentioned, in North America street light is the most common although I would understand lamp post too.

I live in Canada and we use street light as well. But as Paula's comment indicates, anyone would understand either term.

Honestly they are fairly interchangeable and anyone will know what you mean, that being said street light sounds slightly more natural in the US.