A clutch is a mechanical device that provides for the transmission of power (and therefore motion) from the gearbox to the driveshaft when engaged, which can also be disengaged when changing gear.
A little slippage usually leads to more slippage. Slippage increases friction and produces heat. The hotter the clutch gets, the less able it is to maintain its grip and the more it slips. The vicious cycle that results can burn the clutch facings and damage the flywheel and pressure plate. So, the sooner the problem is diagnosed and repaired, the less likely these other components are to be damaged.
No clutch will last forever
The facings on the clutch disc wear as miles accumulate. The clutch pressure plate and flywheel can become scored, worn, warped or cracked from the heat and friction generated by the clutch.
If you can feel the vehicle not pulling when changing gear, it's probably time for a check-up.