Free solo climbing is climbing without ropes, harness, or any protection. The climber relies entirely on their own skill, strength, and judgment — a single fall is fatal in almost every case. This puts free soloing in a different category from every other roped discipline: it is unforgiving in a way that bouldering, sport, and trad climbing are not, even though they all share the same physical movement.
Alex Honnold's 2017 free solo of Freerider on El Capitan — captured in the documentary "Free Solo" — brought the discipline into mainstream awareness. But Honnold prepared for that climb for nearly two years, rehearsing every move with a rope until each section was effortless. Free soloing at any meaningful level requires years of climbing several grades above the route in question, perfect rock, ideal weather, and an extremely calm psychological state. The risk is unforgiving regardless of skill.
Free soloing is not free climbing — those terms are different. Free climbing means using the rope only for safety; free soloing means no rope at all. Most professional climbers do not free solo. Those who do tend to choose routes deliberately well within their physical limits, on rock they know intimately, and even then climbers regularly die in the discipline. Free soloing is not a goal that beginners should hold; it is a specialised pursuit with serious consequences.