In the US the saying 'marquee' is not often employed to describe a short-term outdoor structure, from scout tents to very large two-story temporary buildings are referred to as something -if it is being used for a party then it is a party tent.
A lot of the world follows the US except in the UK along with other areas of Europe there has created a distinction backward and forward terms:
'party tent' is employed for structures in the budget from the market, often made from PE fabric and built with the domestic market in your mind.
'marquee' can be used for your higher end structures well suited for weddings and greater functions.
There remains a considerable middle section of crossover with heavier duty tents and cheaper marquees making the distinction difficult to manage.
Gazebos and canopies are universally smaller often folding structures designed primarily at the domestic consumer. They are built with convenience prioritised over durability, they may be erected in just seconds and due to the clever folding design are put away with all the roof available.
Pagodas (also referred to as witches hats or Chinese hats) may be of variable quality but are distinguished with the pointed shape of the cover. Often employed to make dramatic entrance areas into larger party tents or marquees these is seen because commercial equal of gazebos and canopies.
If you're planning a big formal function by having an attractive entrance then in the united states require a large party tent with pagoda entrance but in the UK demand a large marquee with pagoda entrance!
If you're finally, before using a backyard structure then DIY Marquees offers both marquees and party tents for sale and also gives advice on organising your event and an interactive planning tool to plot your required layout.