Go reflect field index - single index vs. slice

reflect.StructField has an Index field that is typed []int. The documentation on this is slightly confounding:

    Index     []int     // index sequence for Type.FieldByIndex

And of course Type.FieldByIndex follows suit as expected, with the somewhat clearer explanation of its behavior:

    // FieldByIndex returns the nested field corresponding
    // to the index sequence.  It is equivalent to calling Field
    // successively for each index i.
    // It panics if the type's Kind is not Struct.
    FieldByIndex(index []int) StructField

But, there is also Type.Field():

    // Field returns a struct type's i'th field.
    // It panics if the type's Kind is not Struct.
    // It panics if i is not in the range [0, NumField()).
    Field(i int) StructFiel

My question: Exactly for which fields / what circumstances will a reflect.StructField have an Index with len(field.Index) > 1? Is this there to support enumerating embedded fields (reachable through an anonymous field in the parent)? Does it happen in other cases? (ie. is it safe to assume if field.Anonymous, then we can just use field.Index[0] as an argument to Field(i int)?)