LM317T project knowledge

We know that LM317T voltage regulator can give us variable voltage supply....i am recently making a breadboard power supply module in vero board....in the youtube tutorials I saw that people use a LM317T voltage regulator to control the voltage and get variable power supply....my question is why we are using this voltage regulator ic!!! :o .....we can just use a 10k potentiometer...connect the power pins of the potentiometer with my main DC power supply and get the signal pin of the potentiometer to my regulated voltage as povistive pin>>>> is it mandatory to use that ic...or i will face bad effects on my circuit for not using that is....plz tell me soon..


Yes, you can use a pot to create a variable voltage, but you can't power anything with that voltage.
When you do, that voltage will collapse.

Voltage regulators try to keep their output stable, independent of current draw (within reason).

The LM317 is old technology. Needs more than 2volt overhead. And gets hot with current draw (the heatsink tab).
Nowadays we use switching DC/DC regulators for large currents and volt drops,
and low drop-out regulators for small voltage differences.