Do you know the difference between concurrency and parallelism? Did you learn the hard way to how to synchronize stuff after falling victim to deadlocks, data races and instruction reordering? This is a talk about concurrency concepts in general and agnostic on any specific programming language; they differ in how they solve specific problems but the problems to solve are largely the same. I'll try to present a clear mindset of how to reason about concurrency and how to approach problems with concurrency in mind rather than as an afterthought. There will be a lot of storytelling where we dissect non-computer related stuff into concurrent and parallel problems and demonstrate why thinking concurrent can be a useful real-life skill as well. This talk is the first part of two: in Concurrency Explained I'll try to show you to correctly reason about concurrent problems and what approaches you can take, in following Concurrency Applied talk (TBA) we'll delve into technical details of lock implementation, lock-free structures, memory barriers and when it's actually worth caring about them.