This is memory that has recently been used by the kernel and that can be accessed relatively fast.
This is a value used in performance optimization that can be used as the default value to which the results of performance tests can be compared.
This is the I/O scheduler that tries to predict the next read operation. In particular, this scheduler is useful in optimizing read requests.
authoritative name servers
In DNS, this is a name server that has the authority to give information about resource records that are in the DNS database.
This is a system implemented using the autofs daemon and that allows file systems to be mounted automatically when they are needed.