A wingtip is basically what it sounds like, its the horizontal extremity of the wing, and every wing has them.
A winglet is a piece of metal attached to the wingtip, at an angle to the wing itself. These are of very precise design, you can't just slap the things on, the angle needs to be carefully calculated, and the one for the left wing is different to the one for the right wing in the way your left hand is different to your right hand. Wingets have the effect of reducing voritices off the wings, which means that there is less drag. They also effectively increase the sweep and aspect ratio of the wing, without drastically changing its span. A variant of the winglet is Boeing's raked wingtips they are putting on the 767-400
Canard wings are a different kettle of fish completely. They are kind of like the tailplane, except they are forward of the wing, not behind it. This creates an unstable design. With the tailplane behind the wing, when the aircraft pitches up, pressure on the tail plane pushes the tail back up, and returns the aircraft to level flight. However, with canard wings, when the aircraft pitches up, the dynamic pressure on the canards continues pushing the nose up. Thherefore, a small bit of turbulence would very quickly have the aircraft out of control. This is why canard winged aircraft must be computer controlled.
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