Explanation/Reference:
Version 5.1.37-0.1/4 is installed (see note 1 below) and this version can be updated (see note 2 below).
Note:
* 1 The "i" in the I column indicates that these packages are installed in this image.
2 An "f" in the F column indicates the package is frozen. If a package is frozen, you can only install or update to packages that match the frozen version.
* The pkg list command tells you whether a package is installed in the current image and whether an update is available. With no options or operands, this command lists all packages that are installed in the current image. To narrow your results, provide one or more package names. You can use wildcards in the package names. Package variants for an architecture or zone type that does not match this image are not listed.
Reference: Oracle Solaris 11 Information Library, Showing Package Install State Information