The central difference
A trainer replaces the sharpened blade with an unsharpened training blade. A live blade has a functional cutting edge. Both can share similar handle, pivot and balance concepts, but the consequences of a mistake are very different.
For learning
A trainer reduces the risk of cuts and is usually the more forgiving platform for repetitive practice. It does not make flipping risk-free: handles, pivots and hard trainer blades can still pinch or strike fingers.
For collecting
Collectors may value live-blade models for design, maker history, blade steel, finish or rarity. Trainers can also be collectible, especially discontinued versions, limited finishes and historically important designs.
Feel and balance
A trainer and live-blade version of the same family may not feel identical. Blade mass, geometry, handle construction and installed weights all influence balance. Compare the exact configuration rather than assuming every version of a model flips the same way.
Legal considerations
Knife laws vary by jurisdiction and can distinguish possession, carry, sale, transfer and shipping. A trainer may be treated differently in some places, but do not assume that is universal. Check the rules that apply where you live and where a transaction is being shipped.