Blocks are statements surrounded by curly braces, which can contain any number of statements. Blocks are used to group statements and to define the scope of variables. Variables declared within a block are accessible only within that block and are known as block-scoped variables.
Scope pollution occurs when too many global variables are declared, leading to potential conflicts and confusion in a program. It is crucial to avoid scope pollution and practice proper variable naming and management to ensure clean and modular code.