Anna:
First, welcome to this forum and to a highly addictive hobby.
Second, many questions that you ask will have different answers depending where you live. This is one of those questions.
Why? Home Brewing Supply (HBS) shops are more plentiful in Canada than the USA. So mail order is necessary more in the US than in Canada. Also different products are sold in the two countries.
Finally to get to your real question, it is necessary to first clean then sanitize your equipment, etc.
There are a large number of good cleaners. Personally I have been using two. The first is a product called Saniton, that I believe is basically TSP (Tri Sodium Phosphate). For stubborn stains (esp red wine on certain plastics), I use Diversol (a chlorinated product that goes under various brand names).
For sanitizing, I use an iodine based product called Iodophor. Potassium or sodium metabisulphite are more commonly used as sanitizers but their unpleasant arome bothers me. Some people do not like iodophor because it can stain. I have used it a lot (I used to run a Ferment on Premises) without any problems except that it stains badly certain plastics, primarily siphon hose.
Personally I clean after use, and sanitize before use. If an item hasn't been used in some time, I will probably do a quick clean prior to sanitizing as well.
Hope this helps, Steve