What is the difference between <i> and <em> tags, as well as <strong> and <b> tags?

<i> - for stylistic emphasis of text (italic), without semantic load. <em> - for emphasizing text with an accent, indicating its importance or stress (italic).

<b> - for stylistic emphasis of text (bold), without semantic load. <strong> - for emphasizing text, indicating its increased importance or urgency (bold).