I planted a crown of pineapple almost 24 hours ago, today it has been sitting on the windowsill. I am not sure if the roots have already grown up or what is that. I am very interested in growing fruits and vegetables. Any good resource for new beginners?
No, it is not roots. Just loosened fibers from a leaf (top picture) and from the pulp (bottom picture). If you do things right and conditions are optimal then expect it to root within a couple of month. Visible roots will appear within a couple of weeks.
It is easy to find guides like this one.
It is my experience that you should try to remove as much as possible of pulp/fruit and partly dead leaves to avoid rot.