Few
Few is an adjective that means small in number. It is used with countable objects. (गिन सकने योग्य चीज़ों की छोटी संख्या)
E.g.
This department has few employees.
I have few friends in this city.
He ate a few cookies.
Less
Less is an adjective that means small in amount or degree. It is used with objects of indivisible mass. (गिनती नहीं की जा सकने वाली चीज़ की कम मात्रा)
E.g.
Which jar holds less water?
There is less sugar in this tea.
We have less time to finish the project.