I’m doing some board browsing and just the sheer volume of abbreviations and acronyms is a huge hurdle to understanding what I’m reading.
I imagine your course includes free online access to the 'read and learn' portion of the instruction? That will get you grounded in the basics. I'll try to explain a few you might find handy, off the top of my head.
1.) OW - Open Water - the true entry level recreational scuba diving certification. 'Discover Scuba' is more a partial cert. with shallower recommended depth limit and meant for you to dive with a professional, from what I recall. The OW cert. is your doorway to recreational scuba diving.
2.) AOW - Advanced OW - gives you some more dives under professional supervision, an appetizer sampler of some specialties (e.g.: deep - between 60 and 100 feet deep, navigating via compass, etc...). Sometimes requires by dive operators for deeper dives, or who want more seasoned customers.
3.) BCD - Buoyancy Control Device - most first encounter the jacket style, the inflatable vest you wear to achieve neutral buoyancy so you can cover without having to constantly fin up to hold your position. An alternative is BP/W, the back plate/wing system, with a plate over your back to which an inflatable air bladder is secured. The latter is preferred by some people and common in technical diving (which exceeds the recommended limits of recreational diving).
4.) Regulator - the piece of gear between your tank and your mouth. The first stage attaches to your tank, then there's a hose, then the 2nd stage is what is in front of your mouth.
5.) Tanks - AL (aluminum) and steel.
6.) Tank pressure is often given in CF (cubic feet).
7.) SAC - surface air consumption rate, in theory how fast we breathe through your tank's air supply at the surface, but usually corrected for the pressure at the depth we're diving. It's a way of getting a sense of how fast you breathe through your tank, and how that compares to other people.
8.) Viz. - visibility, which I've seen defined as the distance you can make another diver out as such underwater (there may be other definitions in use). Often given as around 30 feet, 50 feet, 70-80 feet or 100+ feet. A rough judgment call.
9.) Dive op. - a dive services provider, such as may run dive boats and take you out to the dive sites.
10.) PADI, SSI, SDI, NAUI and a number of others - organizations offering a range of recreational (and sometimes technical) dive courses, typically leading to certification at some level. At the open water level, which one you use probably won't make much difference. The quality of your instructor, and the effort you put into learning what he/she teaches, is the bigger issue.
Also, let's say you do your training with a dive shop staff member who certifies you through SSI, and you're looking at dive op.s on some island in the Caribbean, and you see they are PADI-affiliated, not SSI. It makes no difference. The shop being a '5-Star PADI facility' has no bearing on whether you can dive with them using your OW cert. that's PADI, SSI, SDI or NAUI. Once you get past OW, some of the specific names of similar courses may differ slightly by agency, but this isn't likely to be troublesome.
Similarly, if you get an SSI OW cert., and want to take a PADI AOW course with another instructor, I don't think you'll have any problem with your OW cert. meeting the pre-requisite requirement. Double-check if that's a concern.
With all the certifications out there, you may wonder how many you 'need,' or should plan to try to get. For mainstream recreational diving, I suggest:
1.) OW - your entry to diving.
2.) AOW - for deeper dives, dives targeting the more seasoned, etc...
3.) Nitrox - helps you get longer deep dives, and is required by some operators for some of their dives.
The Rescue Diver course is good for helping you develop mindfulness and understand what can go wrong and how to react.
