Linux difference in cache and the buff

Both are: buffer
cache is present in the buffer between the cpu and memory, storing the read data from the disk to the
buff is used to store the data block to be outputted to the storage
method of clearing buffer
[root @ DD-Server-9F ~] # echo. 1> / proc / SYS / VM / drop_caches
[the root @ DD-Server-9F ~] # echo 2> / proc / SYS / VM / drop_caches
[the root @ DD-Server-9F ~ ] # echo. 3> / proc / SYS / VM / drop_caches
[the root @ DD-Server-9F ~] # Free -H