You're on a right track - the most useful application of concurrency nowdays is I/O, because of the order-of-magnitude larger latency than CPU. However, concur

You're on a right track - the most useful application of concurrency nowdays is I/O, because of the order-of-magnitude larger latency than CPU. However, concurrency is much more than IO. Concurrency can be best defined as a lack of ordering of computation. For example, you want to compute A, B, C and their values are independent of each other, the order you compute them does not matter - that is concurrency. If your language has means of expressing "compute these things, i dont care about the order", then your language supports concurrency. I suggest reading Communicating Sequential Processes by Tony Hoare. It is a very influential work on concurrency - and the proof of its influence is the design of the Go programming language.