normal NAND gate and Schmitt trigger NAND

What is the difference between normal NAND gate and Schmitt trigger NAND ?
Does it is interchangeable in an application ?

A Schmitt trigger NAND has Schmitt trigger inputs which have hysteresis.

Schmitt trigger - Google Search

In most cases a Schmitt NAND can be used as a normal NAND but an application which requires a Schmitt NAND can't use a normal NAND. There are exceptions of course for example a CMOS gate with Schmitt trigger inputs can't be used as a linear amplifier and will oscillate at a high frequency if you try to do it.

A Schmitt trigger is a level sensitive gate. When the input voltage crosses the critical point, it will fully turn on or off. A normal gate will have problems with a slowly changing input. Check out the link in the previous response for a more detailed answer.