I typed in a huge respose, then got kicked off...aaaargh.
OK, let's try again...
Equipment:
Mask: Modern masks are made of tempered glass and silicone rubber (usually clear), for a good fit (prevents water getting in). The headstrap is adjustable for fit and comfort. Remember, humans are designed to see clearly through air, so you need an air "bubble" to look through. The mask does that. You can spend anywhere from $35 USD (US dollars) to $200+ for a mask with a lens ground to the wearer's glasses prescription. Most divers nowdays just wear disposable contacts inside their masks if they need glasses to see.
Snorkel: A 12 inch or so tube of rigid plastic attached to a flexible tube of silicone (to allow easy adjustment/movement), for an overall length of 20 to 24 inches. Higher-end ones have a valve to allow water to exit (and not enter) near the mouthpiece, and a flapper to prevent waves from washing into the tube from the top. The mouthpiece is thicker silicone rubber. You can spend $15 to $45 on a snorkel.
Fins: Snorkelling fins are like slippers...you just put them on your feet. They are rubber and plastic. You can get diving fins, which are open backed and require a neoprene bootie to be worn with them. This type is generally more expensive due to the cost of the neoprene boot. $35 to $75 USD. You don't need really expensive fins to snorkel, but to dive they are useful if you encounter currents.
Other: If in tropical waters, you may want to wear a t-shirt as well. It prevents injury due to accidental contact with coral, and some areas have "sea lice" that sting you. Sea lice are microscopic jellyfish larvae...their stings are like mosquito bites...they itch and hurt if you scratch. Some people wear nylon "dive shirts" that dry quickly and provide a bit of warmth, but in 80 degree F (27 C) seas, warmth usually isn't a problem...
Skills: You need to be able to float.😉 Really, you should be able to manoever in the water, somewhat better than dog paddle, but that's about it...no need for Olympic-grade swimming skills. You need to check the water conditions relevent to your abilities...You don't want to snorkel in heavy currents if you are not a good swimmer.
Costs: Snorkelling can be done from any beach, but if you are at a resort, at least one guided trip is a good idea. The divemaster (leader) will be able to show you lots of stuff you might miss. Usually $25 will get you an hour off a boat at a great snorkelling place. Otherwise, just find a beach! After you have your equipment, the cost goes down considerably. You can rent equipment at a local place, or from a dive shop in your hometown, but usually it is about $50, and some people don't like to put snorkels used by others in their mouths, even if they are disinfected.
Rules and etiquette: Take a dive flag with you that will float on the surface in the area you are in. Boats/personal water craft are supposed to avoid areas where people are diving and snorkelling. Try not to kick anyone in the face with your fins. Try to avoid standing on any coral....it is fragile, and it could hurt you as it is sharp. Don't crowd in...take turns. Don't annoy/chase the wildlife. Don't get eaten by the wildlife.😉 These two may be related...😉
I don't know much of the history...sorry, you'll need to hit wikipedia for that!
PM me...I have pictures...😉