linux - How "sudo" command works? -

my understand sudo executes given command root privileges, experienced entering command in terminal sudo caches authorization. how works?

for e.g.

sudo fdisk -l [sudo] password xxxxx: 

(once authorize entering password, successive sudo commands not prompting passwords)

sudo fdisk -l 

(not prompting password)

sudo mount -t vfat /dev/sda1 /media/test 

whether sudo wrapper su (substitute/switch user)?

man sudo tell:

   security policies may support credential caching allow user    run sudo again period of time without requiring authentication.    sudoers policy caches credentials 15 minutes, unless overridden    in sudoers(5).  running sudo -v option, user can update    cached credentials without running command. 

it says:

   -k [command]                when used alone, -k (kill) option sudo invalidates                user's cached credentials.  next time sudo run                password required.  option not require                password , added allow user revoke sudo                permissions .logout file.  not security policies                support credential caching.                 when used in conjunction command or option                may require password, -k option cause sudo                ignore user's cached credentials.  result, sudo                prompt password (if 1 required                security policy) , not update user's cached                credentials.