salam it means that you have to post more than 50 relevant and beneficial posts to become a full member, this is to encourage you to post beneficial and on topic posts at all times when becoming a member inshallah wasalam
As the above brother said, you need 50 beneficial posts for a full member. And by that it means not just putting in smileys for one post just to increase your post count. You must be contributive if you can.
You need 100 posts to enter the sisters' section if you wish.