I found it very difficult to differentiate between the various types of dals available. When I cooked, I knew which one to use. But if I had to buy it, I did not know its name. Also some dals looked similar and I was confused when the shopkeeper asked me which one I wanted. So here is a blog to help someone in my condition (specially from my mom)
I have listed 4 important types of dal here.
1. Uddin bele (kannada), ulatham paruppu (tamil), Urad dal (hindi) 
It is dirty white in colour. You get it in oval shape and it is really small in size. You also get broken ones in which the oval shaped dal is in two halves.
Used for making flour (paste) of vada, idli, dosai etc. very good for strong hip bones.
It is dirty white in colour. You get it in oval shape and it is really small in size. You also get broken ones in which the oval shaped dal is in two halves.
Used for making flour (paste) of vada, idli, dosai etc. very good for strong hip bones.
2. Masoor dal (hindi): this is pink in colour. Really tiny. Very easy to identify as it has a distinct pink colour.
3. Kadalai paruppu (tamil), Kadle bele (kannada): Bright yellow in colour.
Hemispherical in shape.used for sambhar, rasam etc.
4. Thoram paruppu (Tamil), thuvar dal (hindi): lighter yellow than the previous one. Also hemispherical in shape, but not as round as the previous one. Flatter compared to the previous one. Used in kootu etc.
The most confusing are the last two types as they look quite similar with a very subtle difference.
