Try It Yourself - SyntaxStudy Editor

HTML / CSS / JS

<!--
    CHILD AXIS (default):
    child::book          = book
    child::*             = * (all element children)
    child::text()        = text node children

DESCENDANT AXIS:
    descendant::title    = all <title> at any depth
    //title              = abbreviated form

PARENT AXIS:
    ..                   = abbreviated parent::node()
    parent::library      = parent if it is <library>

ANCESTOR AXIS:
    ancestor::*          = all ancestor elements

SIBLING AXES:
    following-sibling::book         = next <book> siblings
    preceding-sibling::book[1]      = the nearest preceding <book>

ATTRIBUTE AXIS:
    @id                  = attribute::id
    @*                   = all attributes

SELF AXIS:
    .                    = self::node()
    self::book           = true only if context node is <book>

Combined step examples:
    /library/book/following-sibling::magazine   → m001
    //book[@id='b001']/following-sibling::*     → b002, m001
    //title/parent::book/@id                    → b001, b002
    //book[author='Robert C. Martin']/@category → non-fiction

Namespace-aware:
    //*[local-name()='subject']             → dc:subject element
    //*[namespace-uri()='http://purl.org/dc/elements/1.1/']
                                            → dc:subject
-->