See this page for more details about group management:
https://help.ubuntu.com/lts/serverguide/user-management.html

• Print groups for the current process:
  

  $ groups
  mtitek group1 group2

  
  
• You can print the groups of a specific users:
  

  $ groups mtitek mtitek1
  mtitek : mtitek group1 group2
  mtitek1 : mtitek1

Use the groupadd command to add a new group (man groupadd):

Usage: groupadd [options] GROUP

Options:
  -f, --force  exit successfully if the group already exists

Examples:

• Create a group named "newgroup".
  

  $ sudo groupadd newgroup
  
  $ cat /etc/group | grep newgroup
  newgroup:x:1005:

Examples:

• Delete the group "newgroup":

  $ sudo groupdel newgroup