Concurrency refers to the ability of a system to execute multiple tasks or processes simultaneously, improving efficiency and performance. In software development, concurrency is often achieved by dividing tasks into smaller units that can be executed independently, either on multiple CPU cores or through time-slicing on a single core.

There are several ways to achieve concurrency, including multithreading, parallelism, and asynchronous programming. In multithreading, multiple threads (smaller units of execution) run in parallel, sharing resources like memory. Parallelism focuses on executing multiple tasks at the same time across different processors or cores, while asynchronous programming allows tasks to be executed without blocking other tasks, using techniques like callbacks, promises, and async/await.

Concurrency is critical in applications that need to perform multiple operations simultaneously, such as web servers handling multiple client requests, video games with complex real-time interactions, and systems managing large-scale data processing.

Handling concurrency effectively requires careful attention to thread safety and resource management to avoid issues like race conditions, deadlocks, and data corruption. Programming languages like Java, Python, and Go offer built-in support for concurrency, with libraries and tools that help manage parallel tasks and synchronization.