paninni just means little bread or little loaf ( cant remember which lol ) and are made mostly with either ciabatta or foccacia bread , just personal preference which you use i think :-)
Pane means bread in italian, pannino is a small bread roll, pannini is the plural of pannino. So pannini are just small rolls of any sort. If a ciabatta is made in small bread roll size then they might be called pannini