[git checkout "branch_name"
]
is another way to say:
[git checkout -b branch_name origin/branch_name
]
in case "branch_name" exists only remotely.
[git checkout -b branch_name origin/branch_name
] is useful in case you have multiple remotes.
Regarding [git checkout origin 'another_branch'
] I'm not sure this is possible, AFAK you can do this using "fetch" command
-- [git fetch origin 'another_branch'
]