They are very similar in meaning and usage. An ache is more in the muscles, and a pain can be anywhere. Also, an ache is often times less serious than a pain. Hope that helps!

René is right that an 'ache' is a dull, and often prolonged, pain. For example, if you have to stand for a long time, your legs ache. A pain is sharper, and may last for a shorter time. An ache may also be less severe than a pain.

Great question! They have almost the same meaning, but pain is more commonly used than aching. If you were to use aching, you would say "I'm aching," or even "I'm aching in pain." But, like I said, it's not common. More common would be "I'm in pain," or "I have a pain in my knee (or other location)." This is my take on it, and there are other subtle differences English speakers feel free to add. Side note: Your question would more commonly be said "What is the difference between aching and pain?" Thanks for the great question!

Aching is feeling pain. Aching is a verb. Pain is a noun.

"ache" is a "dull pain"