Memcached timeout

Question

I found sample code about using libmemcached in C/C++. But I don't understand the meaning of two timeout:

1. memcached_timeout of memcached_behavior_set()

2. expire of memcached_set()

   rc = memcached_behavior_set( memc_primary, MEMCACHED_BEHAVIOR_CONNECT_TIMEOUT , memcached_timeout );

   rc = memcached_set( memc_primary, memcached_key_val, memcached_key_len, save_value, strlen( save_value ), expire, 0 );

Could you please explain what they are used for?

Thank you very much!