What is the function of cs0, cs1 in spi?

The spi pin of the jetson xavier nx consists of miso, mosi, sck, cs0, cs1.
Are cs0 and cs1 present to connect multiple slaves when spi is in master mode?
(To connect only one slave, do I need to connect only one of cs0 or cs1?)

Or is cs0 (or cs1) a function to send from master to slave, and cs1 (or cs0) is a function to send from slave to master?

Many devices use CS for synchronization. So suggest to connect CS.