Nodes
Simple explanation
A node is how your program touches the tree: a tiny handle identifying one syntax element, with methods to read its type, span, children, and text. Handles are cheap to copy and never allocate.
Technical explanation
tree/node.zig defines Node { tree: *const Tree, index: u32 }. Every method resolves through the tree's pool: metadata reads are O(1); child/sibling walks are O(degree); descendantForByteRange dives to the smallest covering node. text() slices the tree's owned source. Equality is pointer-plus-index comparison. Because nodes borrow the tree, using one after tree.deinit() is use-after-free — the ownership rules in Memory Model exist to prevent exactly that.