Reading stone with your fingertips and trusting your own placements as you move up vertical rock under your own power.
Rock climbing as a sport was born in Europe in the second half of the nineteenth century. In 1864 gymnasts from Bad Schandau climbed the Falkenstein in Saxon Switzerland, and in June 1886 Walter Parry Haskett Smith climbed Napes Needle in the Lake District, the ascent widely taken as the start of the sport in Britain. The big-wall craft grew up later, in Yosemite. Warren Harding’s team finished the Nose of El Capitan in 1958, after 45 days of climbing spread over eighteen months, and Lynn Hill climbed it free in 1993. That granite is still where the limits move. In January 2015 Tommy Caldwell and Kevin Jorgeson freed the Dawn Wall after 19 days, and on 3 June 2017 Alex Honnold climbed Freerider alone and without a rope, in 3 hours and 56 minutes.
What you can realistically reach: A focused course gets a beginner safely leading easy routes, belaying and building basic anchors — genuine, transferable skills. Self-sufficient multi-pitch and hard grades are seasons of mileage away.
There is a real difference between a school that teaches you and a good-looking website, and too much of the internet is the second kind. Four instruments do the work, and every one of them is visible on the page you are already on.
If a place dodges these, that's your answer. It costs you nothing to ask, and it tells you everything.
This is the short version. The full method is here — the six questions, in order, for any craft anywhere.