A lot of peple have a fascination with brick tea. And a lot of puer is made into brick tea. But many other teas are also made into compressed tea bricks. In fact, compressed tea is one of the oldest forms of tea, dating to the Tang dynasty. The popularity of loose tea came much later. Loose tea is a Ming dynasty tea drinking custom. So too, are gaiwans a Ming dynasty tea custom.
There was still some loose tea available in Tang China. But it just wasn't as popular back then as brick tea.
Today, you can still find compressed teas made from green teas, black teas, red teas, oolong teas. So there are quite a variety of brick teas other than puer.
It's puer (the modern, Pinyin spelling), or puerh (the older Wade-Giles spelling). In Cantonese you would spell it polei or ponei.
Actually, puer has been around since the Tang Dynasty. But there are so many other kinds of brick tea, that we shouldn't overlook them when discussing brick tea.
Do you know the proper way to brew compressed tea is to simmer it, not steep it? This is because the leaves are so tightly compressed together; they need the gentle force of simmering water to express the essence in the leaves.
You could still steep it to get a decent cup, but you will see a color change at the bottom of the cup, because the essence is still trying to be expressed from the leaves. So infusion is just too weak a method to brew brick tea.
Anyway, brick tea is popular with China's ethnic minorities that live in the mountainous areas. And at high altitudes, water boils at 80 C, instead of 100 C. So the water is much cooler - too cool for effectively steeping brick tea. Therefore, they have the practice of simmering their brick tea. That's another reason why brick tea enthusiasts simmer their tea – in accordance with the custom of the ethnic minorities who live in the mountains.