diff --git a/source/file.go b/source/file.go
index 2bd6d2e1c..469c35eee 100644
--- a/source/file.go
+++ b/source/file.go
@@ -21,72 +21,86 @@ import (
 	"github.com/spf13/hugo/helpers"
 )
 
+// File represents a source content file.
 // All paths are relative from the source directory base
 type File struct {
-	relpath     string // Original Full Path eg. content/foo.txt
+	relpath     string // Original relative path, e.g. content/foo.txt
 	logicalName string // foo.txt
 	Contents    io.Reader
 	section     string // The first directory
-	dir         string // The full directory Path (minus file name)
+	dir         string // The relative directory Path (minus file name)
 	ext         string // Just the ext (eg txt)
 	uniqueID    string // MD5 of the filename
 }
 
-// UniqueID: MD5 of the filename
+// UniqueID is the MD5 hash of the filename and is for most practical applications,
+// Hugo content files being one of them, considered to be unique.
 func (f *File) UniqueID() string {
 	return f.uniqueID
 }
 
+// String returns the file's content as a string.
 func (f *File) String() string {
 	return helpers.ReaderToString(f.Contents)
 }
 
+// Bytes returns the file's content as a byte slice.
 func (f *File) Bytes() []byte {
 	return helpers.ReaderToBytes(f.Contents)
 }
 
-// BaseFileName Filename without extension
+// BaseFileName Filename without extension.
 func (f *File) BaseFileName() string {
 	return helpers.Filename(f.LogicalName())
 }
 
-// Section The first directory
+// Section is first directory below the content root.
 func (f *File) Section() string {
 	return f.section
 }
 
-// LogicalName The filename and extension of the file
+// LogicalName is filename and extension of the file.
 func (f *File) LogicalName() string {
 	return f.logicalName
 }
 
+// SetDir sets the relative directory where this file lives.
+// TODO(bep) Get rid of this.
 func (f *File) SetDir(dir string) {
 	f.dir = dir
 }
 
+// Dir gets the name of the directory that contains this file.
+// The directory is relative to the content root.
 func (f *File) Dir() string {
 	return f.dir
 }
 
+// Extension gets the file extension, i.e "myblogpost.md" will return "md".
 func (f *File) Extension() string {
 	return f.ext
 }
 
+// Ext is an alias for Extension.
 func (f *File) Ext() string {
 	return f.Extension()
 }
 
-// Path the relative path including file name and extension from the base of the source directory
+// Path gets the relative path including file name and extension from
+// the base of the source directory.
 func (f *File) Path() string {
 	return f.relpath
 }
 
+// NewFileWithContents creates a new File pointer with the given relative path and
+// content.
 func NewFileWithContents(relpath string, content io.Reader) *File {
 	file := NewFile(relpath)
 	file.Contents = content
 	return file
 }
 
+// NewFile creates a new File pointer with the given relative path.
 func NewFile(relpath string) *File {
 	f := &File{
 		relpath: relpath,
@@ -100,6 +114,8 @@ func NewFile(relpath string) *File {
 	return f
 }
 
+// NewFileFromAbs creates a new File pointer with the given full file path path and
+// content.
 func NewFileFromAbs(base, fullpath string, content io.Reader) (f *File, err error) {
 	var name string
 	if name, err = helpers.GetRelativePath(fullpath, base); err != nil {