74LS00 is a member of 74XXYY IC series. The 74xxyy ICs are logic gates of digital electronics. 74LS00 IC has four NAND gates. Also each gate has two inputs.
74HC14 is a member of 74XXXX series ICs, which consists of LOGIC GATES. 74HC14 IC has six NOT gates with SCHMITT TRIGGER. Hence name HEX INVERTING SCHMITT TRIGGER.