The type of stone refers to the material it is made with. You can find many different types, including diamond, ceramic, natural stone, and synthetic. I would only suggest diamond if you’re planning to be sharpening only ceramic knives. Many of the stones you’ll find on Amazon or other retails are made of Corundum, which is a crystalline form of aluminium oxide. It’s a fine choice for a beginner sharpening stone.
One thing about this stone is that it is very "thirsty." I had a cup of water close by just to add a little water periodically when it felt like it was scraping a little too aggressively. Also, be sure to do as the instructions say and use different parts of the sharpening surface. I wasn't paying attention the first few minutes, and apparently I would end each sharpening pass in the exact same spot, creating a very very small notch on the edge of the stone. So I turned the stone around and made sure to vary the ending spot, and it seemed to buff out that little notch very quickly. My knife is now incredibly sharp--it seems to glide through material rather than "cut" it. I know some people would continue to go even higher with the grit, but for my purposes this whetstone is just perfect. I'll be tackling the kitchen knives next!
Frequently, our recommendation for beginning sharpeners is to start with diamond stones as their strengths make them ideal to build a sharpening toolkit around. Diamond stones are low maintenance and durable, lasting many years with only occasional cleaning. They are among the fastest stones to use making them time efficient. Diamond grit will handle even very hard steels, and diamond stones can be used for flattening waterstones. All these things make diamond stones a practical foundation for your sharpening toolkit.
A single stone of 120 grit and a combination stone of 1000 and 3000 grits come along with a stone holder all for a price of less than many other individual stones. The stones are 6 7/8" long and 2 1/8" wide. A flattening stone of some kind would be needed, but with economical options available in those, the overall price of this kit would still be low. This entry level set is a good budget minded option.
In most cases, the sharper, the better. The sharpness of your edge is determined by the angle (the lower the angle, the sharper the edge) and how fine of a grit you choose for your final honing. Since you have already determined your angle many steps earlier, now you just need to know which grit you can stop at. This again depends on the use of the knife. In most cases, go all the way to the finest stone that you own as this will give you your best edge. The only exception would be a knife used to cut soft vegetables like tomatoes, as a slightly more coarse edge will provide more of a tooth pattern for easier cutting.
My first set of sharpening stones so I have nothing to compare them to. For $50, though, great price to get into the world of sharpening. Stones are great and easy to use. Was able to put hair shaving edges on knives. Took a couple of knives to feel comfortable and better with the process and how to sharpen, but the stones you get work great. Here's the secret though. Get the green leather stoping block as well. As great as the stone are, I have found that stroping the knife after the fact is what really brings out that razor edge. And after using the knife, stroping it again, will restore and keep it razor sharp. Hope you enjoy it as much as I am.