A trick might be something special you can do, that entertains other people. The dolphins in the picture are performing tricks.
A trick is also a sneaky way of doing something, by making people think you are doing one thing when in fact you are doing something else. For example, you might trick someone into giving you something by telling them a lie.
A trickle is a thin stream of water. A trickle is slightly more than a drip but much less than a full stream of water. The waterfall in the picture is only trickling because there hasn't been much rain.
A trickle is often used to describe a small amount of something passing by, as in "he was earning a trickle of money from his second job".
