The simplest way to build a parser.
A recursive descent parser is a top-down parser as it starts from the top or outermost grammar rule and works its way down into the nested subexpressions before finally reaching the leaves of the syntax tree.
It’s called “recursive descent” because it walks down the grammar.
In a top-down parser, you reach the lowest-precedence expressions first because they may in turn contain subexpressions of higher precedence.
LL(1)
( parser )
Tokens -> Tree -> Compiler / Interpreter
A definition of the syntax of a language.