i would say you could make four basic categories
commericial
military
recreational
technical
The first two are obviously specialist and despite some peoples best efforts they should not be confused even with technical diving. Some aspects of commercial diving may overlap with technical but they are different and should not be considered in this argument.
recreational - simple dive plan and non decompression (dont bother flamin gon this one), that is to say you may make a direct ascent to the surface, usually with a safety stop at 5m.
Technical - more complex dive plan, with some form of decompression required either using back gas or possibly using an oxygen rich decompression gas. As stated before this is usually termed as a ceiling either real (like a cave or a wreck) or theoretical the decompression stop.
commericial
military
recreational
technical
The first two are obviously specialist and despite some peoples best efforts they should not be confused even with technical diving. Some aspects of commercial diving may overlap with technical but they are different and should not be considered in this argument.
recreational - simple dive plan and non decompression (dont bother flamin gon this one), that is to say you may make a direct ascent to the surface, usually with a safety stop at 5m.
Technical - more complex dive plan, with some form of decompression required either using back gas or possibly using an oxygen rich decompression gas. As stated before this is usually termed as a ceiling either real (like a cave or a wreck) or theoretical the decompression stop.