This sitting pose is a moderate variation of the full “lotus pose”. There are two options; bend one leg and place the foot of the bend leg on top of the opposite thigh. The other leg is bent, bringing the heel towards the buttocks, as in A. Or you can sit on the heel of the other leg as in B. And as in all the sitting poses keeping the spine straight is very important. It doesn’t matter which leg you choose to place on top of the opposite thigh, you can practice with both.
This pose is not advisable for people with knee injuries.