Inline Skates or Rollerblades (called after the company who widely promoted inline skating) are somewhat similar to roller skates but instead of having two front and two rear wheels, inline skates have two, three, four or five wheels arranged in a single line.
Some have a brake or stop usually at the heel end of the skate.
Developed as a substitute for ice skates by Russian athletes wanting to train on ground for speed skating at the next Olympics, they became popular in the late '80s early '90s.

The first patented Roller Skate was by a Belgian man named John Joseph Merlin in 1760.
The Roller Skating Rink Operators Association was developed in 1937.

As with all sports there is a room for getting hurt, so Protective Gear is a must.
Knee and Elbow guards, gloves and a good quality helmet are investments that should be seen as minimum safety equipment.

History of roller skating: Wikipedia

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