Types of Protection
The standard disclaimers about how dangerous climbing is and how unreliable anything is you read anywhere apply here as well. This site is far from definitive (and probably far from accurate). It is here for the amusement of myself and friends and possibly to shed some light, though I don't mind a little obfuscation now and again either. Various parts have been adapted and pilfered from sources found hither and yon, though I have tried to make all entries mostly original. So please read, but remember that responsibility for safe climbing is your own.
1. Bolted (or "sport" climbing)
Used on friable rock (i.e. Limestone) in the UK and everywhere on the continent. Every so often (we'll come back to that) on a route a bolt (basically a ring or plate you can clip into) is securely fastened (we'll come back to that too) into the rock. As the leader climbs he clips one end of a quickdraw into the bolt and the other end into the rope. At the top there is either a ring or a screwgate or similar, and the belayer lowers the leader from that.
Every so often can vary from every couple of feet (potential 6 foot fall - safe and no-ones going to get hurt) to every 20 or 30 feet or more (60ft fall. Scary and bloody dangerous).
Securely fastened can vary from a brand new hanger secured by a half-metre long expansion bolt driven into the rock to an almost-rusted-through dodgy bit of 50 year old iron attached to a similarly ancient iron spike driven in between two boulders, one of which is precariously balanced and/or moveable by hand. The rings or screwgates at the top are sometimes missing.
The leader climbs clean (i.e.unbolted, unspoilt) rock. As well as quickdraws, he carries nuts (basically small lumps of metal on a wire), rocks (larger lumps of metal on a wire) or cams (mechanical devices that expand) up with him. At suitable intervals (we'll come back to that) he places the protection securely (we'll come back to that too) in cracks and other natural features on the rock and clips the rope in to them. The idea is that if a fall is taken the gear will jam against the rock and hold the fall.
Gear/Protection: What you can put in to hold a fall.
Gear rips: Gear pulls out as the load from the falling climber comes onto it. i.e. does not hold a fall, though it might slow you down.
Good gear: Probably going to hold
Poor gear: Probably not going to hold.
Bomber gear. More or less certain that it will hold a big fall.
Run-out: The distance between the gear and the climber - i.e. half the length of the potential fall.
Deck-out: A fall that will end by the climber hitting the ground.
How often the leader places protection is entirely up to the leader and what is available in terms of natural features. On a decent, well cracked rock, you might be able to put protection in every six inches. No-one does this. Most people I've observed put in gear every 10-20ft if climbing happily, every couple of feet if worried they are going to fall off. It depends on the climber. A worried or safe person will put more gear in than a "bold" or confident person. Saying that, placing gear requires you to hang off one hand, using the other to place the gear - its tiring, so most gear placement are a compromise between how tired you are and how worried you feel.
This, of course, depends on there being places to put the gear. On some routes, there is no gear. i.e. there is no place where you can lodge any lumps of metal or similar. Many smooth flat slabs are a classic case in point. This is where a climb gets described as "bold" - ie. there is considerable run-out, the potential fall is large, and there's nothing you can do about it.
Gear placement is a skill, learnt by experience. Poor placements can "rip".
The typical British climb is described as "No Holds, poor gear, very run out and horrendous landing".
There is another religious debate between bolting and traditional climbing.
The traditional climber says that the ethic should be to leave the rock how it is found. We have a finite amount of good climbing rock in the world and we should endeavour to leave it as much as possible how we found it, both from the point of view of an individual climber and climbing generations. If you can't do a route or are unhappy with the protection, leave it until you get better. Don't try and change the characteristics of the rock or route just because of your lack of skill.
The bolted climber says the climb should be safe, and that bolts open up climbing to people with little experience
On the continent, most stuff is bolted, and that is the accepted way. However sometimes a landowner who doesnt want people to climb will come along and chop the bolts off. Which is nice as if not noticed at the beginning of the climb potentially leaves the climber with no protection from a fall.
In the UK, Gritstone is NEVER bolted. Friable rock MAY be. The argumentative sort would also shy away from suggesting that a particular gritstone crag be bolted. In additoin to the blood on the carpet, walls and ceiling, there would likely be a posse waiting for them round their house, which would have been burnt to the ground.
One guy once posted to UKClimbing.com with "I've found this gritstone crag and I am going to bolt it" 200 messages suggesting that the guy be, basically, strung up, turned up within 5 mins.