Syntax is keywords, reserved words, building blocks of a programming language.
... but what is 'word', what is 'alphabet' ... what is 'pattern', what is 'grammar' ... in Computer Sciences?
... there's Lecture: 'Languages & Automatons' that answers these and other questions.
... beside keywords are variable identifiers, constants, etc ... that can't have the same 'names' as keywords.
Semantics.
Semantics is 'meaning'.
Instruction's semantics is what it precisely does ... how it 'works internally' ... what 'magic' occurs when instruction is executed ... 'method call' or 'method invocation' is also instruction, for example.
Magic is something that works ... somehow, not sure how ... sometimes not the way we want, sometimes there are errors or other problems ... but occasionally it works 'well enough', 'the way we prefer'.
Not many understand magic, esoterics, spirituality ... so many details, that make no sense to most.
Hardware, Operating System, 'internet configuration', etc, ... many more factors do affect how the same instruction works on different machines.
'u mnie działa'.
... ;)