The normal charmed condition only generates friendly feelings.
- A charmed creature can't attack the charmer or target the charmer with harmful abilities or magical effects.
- The charmer has advantage on any ability check to interact socially with the creature.
As an enhancement to Channel Divinity: Charm Animals and Plants gives you an extra option - issuing instructions.
Master of Nature
At 17th level, you gain the ability to command animals and plant creatures. While creatures are charmed by your Charm Animals and Plants feature, you can take a bonus action on your turn to verbally command what each of those creatures will do on its next turn.
It is different from Dominate Person, because issuing instructions takes a bonus action and has to be done verbally (Dominate person is telepathic and doesn't take an action). If Master of Nature was meant to have the total-and-precise option that Dominate Person does, it would say so.
Like most things in 5E, it does what it says on the tin... You spend a bonus action to give instructions, and the subject obeys on its next turn. The subject doesn't even get a new save or anything like that.
It's worth noting that Channel Divinity: Charm Animals and Plants is different from, and somewhat more fragile than, Charm Person, too. Charm Person breaks if the subject's new friends do any harm to it, the Channel Divinity breaks if the subject takes any damage. On the flipside, it's more powerful in a different way, because it has a 30' radius and potentially affects every plant and beast in the area.