You mean simply climbing out of the saddle? Or something different?

Seated and standing pedaling use slightly different muscles. So switching between the positions gives a bit of a rest to some muscles while others are working.

You need to shift to a higher gear, like 2 cogs smaller, when standing, and use a lower cadence. For example if you are climbing seated in 53x26, before standing you would shift to 53x21 or something like that. Climbing speed will be the same.

If you do not shift when changing to the standing position, your speed will be lower. It will be easier, so you might initially feel like you are getting a rest, but if you don't have enough resistance at the pedals, standing pedaling gets tiring very fast.

A variation of this is to stay seated, but alternate between sitting on the noise of the saddle and on the tail of the saddle. Again, slightly different muscles are being used.