The term has never confused me. Required: Do it. Safety: For your safety. Stop: Stop ascending and hold for the recommended period of time. What is confusing about this? Sure there are allegedly "safety stops" that are "optional." I don't even know what that means without training to understand when it is better to get out of the water without a safety stop.
[fireproof suit]
Since this has become part of the discussion, it might be helpful for us to agree on a few definitions, just so everyone is using the terms the same way for the sake of this discussion. Although I think I've captured how many people use the terms, not everyone or all agencies necessarily agree completely, so don't assume these are universal definitions.
Recreational diving (diving within recreational depth limits, generally 130', and within NDLs) includes the implicit assumption that you can always ascend directly to the surface without stops, with 'minimal' chance of a problem.
Once you exceed recreational depth or time limits, you're into
decompression diving, that is diving where stops are
mandatory (or other profile shaping techniques such as ascent rates) or else bubbling sufficient to cause clinical symptoms is 'probable'. Generally, most tech-oriented instructional agencies strongly recommend/require redundant breathing gas supplies and regulators on each diver, since the failure rate is frequent enough to be an issue.
Most people define a
safety stop as being a stop which is always optional (i.e. not mandatory), although highly recommended. As some of the researchers and originators involved have posted elsewhere on SB, quantitatively measured, safety stops in themselves do not appear to have a large or maybe even measurable effect on the frequency of DCS. However, there are theoretical reasons to believe they may have some benefits, and given the difficulties of measuring or even determining the effects on humans, most people use them as standard practice. They haven't always been there, there was some debate when people started using them, and some people don't believe in them. Some SB members have described in the early days how a large part of the value of the stop was actually to help make sure ascent rates stayed below table assumptions and make sure people were under control before undertaking the most critical part of the between 15-30' and the surface.
Part of the conflict in terms is created when you see the term
decompression. All dives involve pressure change and therefor decompression, but for most people, the term
decompression stop means a mandatory stop.
The biggest conflict in this thread seems to be caused by the term "mandatory safety stop". Quite a few people are of the school of thought that if the stops are mandatory, you're no longer recreational diving since you can no longer ascend directly to the surface if there are any problems (gear or otherwise) and you should have redundant gas supplies and regulators. However, if the table publishers are including these as a way to create additional safety margin and not a true absolute requirement, then some would argue that it really is a safety stop, and that the term "mandatory" is not in line with how the majority of divers with the more extensive technically training use the term.
[/fireproof suit]