"It's nice!". Combination of the words it is and nice. Used as a quicker and more casual pronunciation of "it's or it is nice".
Proper pronunciation: "I love the layout of their living room, it is nice". Social pronunciation: "I love the layout of their living room, s'nice".
Something far superior to "nice"
"I finally had sex with my girlfriend last night."
"Then her sister came in and joined."