Ok, so after looking through my game and rulebook and I read the "Triggered and Continuous Effects" section and all the examples you gave ("at the beginning of your turn, When this card enters your Stable, discard a card, you may sacrifice this card") are triggered.
The last two are triggered because "Some triggered effects are mandatory (ex. 'If this card is in your stable at the beginning of you turn, DISCARD a card'), while others are optional ('If this card is in your stable at the beginning of your turn, you may STEAL a Unicorn')"
The other two are triggered because triggered effects can also be preceded by a "when" like in your example ("Triggered effects are always preceded by an 'if' or 'when.'"). Some more proof that are triggered is that the next paragraph states that "Any effect on an Upgrade card, Downgrade card, or Unicorn card that is not a triggered effect can be assumed to be a continuous effect. A card's continuous effect is active as long as that card is in a Stable (unless otherwise stated)." and none of the examples you gave up in your question are continuous so therefore they must be triggered.
As for your "in other words", it's not the same because unicorn cards like the Queen Bee Unicorn can have continuous effects (If you're wondering what the Queen Bee Unicorn's effect is, it's "Basic Unicorn cards cannot enter any other player's Stable").