Declarative programming

Declarative programming is a paradigm focused on describing a program's logic instead of particular executional steps. In other words, in declarative programming, we define what we want instead of how we want it. In contrast to imperative programming, programs in declarative programming are defined with expressions instead of statements.

Very common examples could be SQL and HTML languages. Consider the following database query:

SELECT * FROM user WHERE id = 42 

In SQL, we define what data from what table we want to query, but the implementation details are completely hidden for us. We don't even want to worry about how the database engine stores or indexes the data.

In HTML, we define the structure of elements; what's behind the browser's rendering process isn't important for us. We just want to see the page on the screen.