scala> import scala.collection.immutable.{Seq=>ISeq}
import scala.collection.immutable.{Seq=>ISeq}

scala> val seq = Seq(1,2)
seq: Seq[Int] = List(1, 2)

scala> val iseq = ISeq(1,2)
iseq: scala.collection.immutable.Seq[Int] = List(1, 2)

scala> :type -v seq
// Type signature
Seq[Int]

// Internal Type structure
TypeRef(
  TypeSymbol(
    abstract trait Seq[+A] extends PartialFunction[Int,A] with Iterable[A] with GenSeq[A] with GenericTraversableTemplate[A,Seq] with SeqLike[A,Seq[A]]

  )
  args = List(
    TypeRef(TypeSymbol(final abstract class Int extends AnyVal))
  )
)

scala> :type -v iseq
// Type signature
scala.collection.immutable.Seq[Int]

// Internal Type structure
TypeRef(
  TypeSymbol(
    abstract trait Seq[+A] extends Iterable[A] with Seq[A] with GenericTraversableTemplate[A,scala.collection.immutable.Seq] with SeqLike[A,scala.collection.immutable.Seq[A]] with Parallelizable[A,scala.collection.parallel.immutable.ParSeq[A]]

  )
  args = List(
    TypeRef(TypeSymbol(final abstract class Int extends AnyVal))
  )
)