Jnana mudra is a hand position used during meditation and breathing practices. Touch the tip of each index finger to the tip of the thumb, forming a circle, and let the other three fingers extend without strain. Rest your hands on your knees or thighs with your palms facing down. As you notice your breath, the contact between thumb and finger can offer a place to return your attention.
The Sanskrit name joins jñāna (gyan), knowledge, with mudra, gesture. You don't need to believe the gesture will make you wiser. Treat it as a small reminder to stay curious and notice what is already here.