Have you ever heard anyone order Orange Pekoe tea? Yeah, I’ve done it myself, usually it means you just want plain black tea, but apparently Orange Pekoe isn’t a type of tea at all, rather, it’s a grade of tea leaf.
In other words, Earl Grey, a blended black tea, would be considered Orange Pekoe, due to the size of the leaves used to make the tea blend, if they were Orange Pekoe grade.
Tea grading is done according to leaf size, from the buds at the top of the plant, to the leaves at the bottom. Orange Pekoe is the highest category, however, there are higher gradings withing the Orange Pekoe category. Next there is Broken Leaf, and below that there is Fanning and Dust.
Here’s a great guide for more info: Tea Terminology
So, what do people mean when they order ‘Orange Pekoe’? Probably the same as me, I was raised on the Canadian classic Red Rose, a type of orange pekoe black tea. It is ubiquitous in my area, bought in large quantities is a beautiful deep red box with a large proclamation of being Orange Pekoe. Since Red Rose is the brand, people just grew accustomed to calling the tea ‘Orange Pekoe’ and it stuck.