When buying a climbing rope you will need to make a number of decisions about the type of rope you need. Dynamic or Static? Single or Half? Dry Treated or Standard? 50m or 60m (or for that matter, 30m, 40m, 70m or 80m?).
Single Ropes are ropes designed to be used on their own and are mainly used on bolted routes at walls and on sport climbs. They can also be used on easier trad climbs but may slightly reduce the protection possibilities. They can be paired up with another rope and used as a Half Rope and so a Single rope is probably the best buy as a first rope. In many sport climbing areas these days routes can be 35m or even 40m long so a 70m or 80m rope is increasingly the length of choice.
Half Ropes are designed to be used in pairs and are mainly used for trad climbing, where the leader is responsible for placing their own protection. For summer rock climbing, 50m ropes are long enough and they would not normally be any thinner than 8mm, but in winter, 60m ropes are worth having and as light as possible - these will often enable you to reach a safe belay that you could not get to with 50m ropes.
Those wanting a rope for winter and/or alpine climbing should go for a Dry rope - a standard untreated (or Non-Dry) rope will soon cause problems on snow as it can be impossible to get it though a belay plate once it becomes waterlogged and then frozen. Semi Dry ropes (marketed under various names like "Dry Cover") are those that have just the sheath dry treated but not the core - this treatment is intended to give extra longevity.
For more information about ropes please see our Climbing Ropes page.