Strep Throat is a really common bacterial infection, and since it's bacterial it responds (usually very quickly) to antibiotics. You catch it the same way you catch a cold or the flu... from breathing in air from someone else who has it, or via contact (like sharing a drink, unwashed hands, etc.).
Common symptoms are white pustules (white lumps) in the back of the throat, a metallic & putrid smell, swollen & red throat/tonsils, fever, body aches, etc. You can get a strep infection anywhere, but it's most common to get it in your throat.
The most commonly Rx'd antibiotic for strep is Amoxicillin, although others are also used. It's very VERY important to finish the entire round of antibiotics, even though you'll probably be feeling fine for weeks... in order to avoid making a super-strain that doesn't respond to the antibiotic. Strep is also really intolerant of salt. So in addition to the antibiotics, it's recommended that a person with strep throat gargle salt water several times a day. For those of us who are prone to strep, gargling saltwater when the first tickling of the throat starts, and actually wipe out an infection before it has a chance to get too strong. Toddlers can have a difficult time gargling without swallowing (and swallowing saltwater makes you throw up). So when kiddo was too young to gargle, I'd give him super salts fries from McDonalds when he was sick with strep. (I'd also spray his throat down with chloraseptic to numb it so he could drink/swallow without pain... but chloraseptic is something some parents don't like).
With antibiotics & salt water gargling; strep throat usually lasts about a week to 10 days. Without antibiotics strep throat can last for several weeks to over a month and can continue on into other systems. Scarlet Fever is a more advance strep infection, and can cause (amongst other things) permanent heart damage. So you REALLY want to hit strep with antibiotics as early as possible, and finish the entire course.