Haskell is a purely functional programming language with strong static typing and lazy evaluation. It was named after the logician Haskell Curry and is known for its expressive type system and mathematical foundation. Haskell is widely used in academia and industry for its ability to handle complex problems with concise and maintainable code.

1. Purely Functional: Functions in Haskell are pure, meaning they do not have side effects. This makes reasoning about code easier and leads to more predictable and reliable programs.
2. Strong Static Typing: Haskell's type system catches many errors at compile time, reducing runtime errors and improving code safety.
3. Lazy Evaluation: Haskell evaluates expressions only when their values are needed. This can lead to performance improvements and allows for the creation of infinite data structures.
4. Immutability: Data in Haskell is immutable by default, which means once a value is assigned, it cannot be changed. This leads to safer and more predictable code.
5. Type Inference: Haskell can often infer the types of expressions automatically, reducing the need for explicit type annotations and making the code cleaner and easier to read.

• Conciseness: Haskell allows you to express complex ideas with less code compared to imperative languages.
• Maintainability: Pure functions and immutability lead to code that is easier to test, debug, and maintain.
• Concurrency and Parallelism: Haskell's abstractions make it easier to write concurrent and parallel programs.
• Academic and Industry Use: Haskell is used in both academic research and industry applications, particularly in areas requiring high reliability and correctness.

• Web Development: Frameworks like Yesod and Servant allow for building robust web applications.
• Data Analysis: Libraries like Haskell's Data Analysis and Visualization (HADaV) provide tools for data manipulation and visualization.
• Financial Systems: Haskell's strong type system and reliability make it suitable for financial applications where correctness is critical.
• Compilers and Interpreters: Haskell's expressive syntax and powerful abstractions make it a popular choice for writing compilers and interpreters.

Let's start with a simple "Hello, World!" program to get a feel for Haskell's syntax.

• main :: IO (): This line declares the type of the main function. IO () indicates that main is an I/O action that returns a unit type ().
• main = putStrLn "Hello, World!": This line defines the main function. putStrLn is a standard library function that takes a string and prints it to the console.

1. Install the Haskell Platform (if you haven't already).
2. Create a new file named HelloWorld.hs.
3. Write the "Hello, World!" program as shown above.
4. Open your terminal or command prompt.
5. Navigate to the directory containing HelloWorld.hs.
6. Compile the program using the GHC compiler:

   ghc -o HelloWorld HelloWorld.hs
   

7. Run the compiled program:

   ./HelloWorld
   

In this section, we introduced Haskell, a purely functional programming language known for its strong static typing, lazy evaluation, and immutability. We discussed its key features, practical applications, and wrote a simple "Hello, World!" program to get started. In the next section, we will set up the Haskell environment to begin writing and running Haskell code.