Rigveda, Yajurveda, Samaveda and Atharvaveda are the four Vedas. In the traditional classification, Vedic literature belongs to Shruti. Shruti is a category; it is not the name of a fifth Veda.
Samhita, Brahmana, Aranyaka and Upanishad describe important textual forms or layers associated with Vedic traditions. A simple tree helps a beginner, but individual works can be embedded in other works and their boundaries can overlap.
A careful edition records its Veda affiliation, recension and source. An introductory explanation helps you orient yourself; it does not replace a complete edition or specialist instruction in accented recitation.