Pallavi. This is the equivalent of a refrain in Western music, with 1 or 2 lines. Anupallavi. This is the second verse, also as 2 lines. Charana. The final (and longest) verse that wraps up the song. The Charanam usually borrows patterns from the Anupallavi. There can be multiple charanas.
the three layers of a typical carnatic piece are
Pallavi pallavi pallavi Anupallavi Anupallavi Charana Charana charana