The roller skate is a type of skate with wheels to be used on solid ground (as opposed to the ice skate which is to be used on ice. The two main forms of roller skate are the quad skate, which has its four wheels arranged in two rows, and the inline skate, which has its wheels in a line.
The sports associated with this form of skate are collectively known as roller skating (usually associated with the quad skate) or inline skating (usually associated with the inline skate).
Although inline skate designs were invented as early as the 18th century, and one version was patented in France in 1819, their use was relatively unknown until the early 1980s. This was largely due to the fact that these early inline skates of the 18th and 19th centuries were not very manoeuvrable. It was very difficult with these skates to do anything but move in a straight line and perhaps make wide sweeping turns.
The quad skate was first designed in 1863 in Massachusetts to attempt to change this. It was a huge success, living up to expectations; by the 1880s roller skating had become a popular pastime. The design of the quad skate has remained essentially unchanged since then, and in fact remained as the dominant roller skate design for a hundred and fourty years.
It was not until 1979 that Scott Olson and Brennan Olson of Minneapolis, Minnesota came across a pair of old inline skates and, seeing the potential for off-ice hockey training, set about re-designing the skates using modern materials and attaching ice hockey boots. A few years later Scott Olson began heavily promoting the skates and launched the company Rollerblade, which name many people often use when referring to inline skating, no matter what brand of skate they use.
For much of the 1980s and into the 1990s, inline skate models typically sold for general public use employed a hard plastic boot, similar to ski boots. But in about 1995, "soft boot" designs were introduced to the market, primarily by the sporting goods firm K2 Inc., and promoted for use as fitness skates. Other companies quickly followed, and by the early 2000s the use of hard shell skates became primarily limited to the aggressive skating discipline.