Grinding is a kind of dance where two people stand very close to each other and move their bodies in a way that looks like they are rubbing against each other. It is usually done at parties or clubs where there is loud music and lots of people dancing.
When two people are grinding, they stand facing each other and the person in front will usually lean their back against the other person's front. Then they will move their hips in a way that looks like they are rubbing against each other. The person behind may put their hands on the other person's hips or waist to help guide the movement.
It's important to remember that grinding is just a type of dancing and it's only meant to be done with someone who has consented to dance with you in that way. It's also important to keep in mind that not everyone likes grinding and it's always important to respect other people's boundaries and comfort levels.