The vital role punctuation marks play in giving meaning, direction and flow to any writing cannot be over emphasised. A carelessly placed comma, hyphen, semi-colon, full colon or quotation mark can significantly alter the intended meaning.
Commas are used to introduce a new part to a sentence. The semi-colon is used to join two sentences, and can be used in lieu of a conjunction. The full colon is used to introduce a clause that explains the preceding one. For instance, ‘He carried the whole war chest: machetes, arrows, bows and spear’.