Saying you want to buy a flagpole is a bit like saying you want to buy a car.  Do you want a budget hatchback or a Rolls Royce?  Both are cars, but there is a big difference!

Options include things like tapered or untapered, spigot bases, with or without ground sleeves or flange bases, internal or external halyards etc., accessories include things like flash covers, ground sleeves and caps and spares parts are self explanatory!

What is a halyard?

It is a nautical term derived from the command to Haul a Yard.  Put simply it is the rope that hauls the flag aloft.