Veda are Shruti scripture and is said/believed that Rishi in the state of Sadhana or samadhi heard Vedas directly from Parabrahma/Parameshwara, so, simply means Vedas are not created by man and our sages are not authors or writer of Vedas, There are four Vedas :
Vedas are basically classified into two categories:
Samhita is the core part of Veda (which is heard by Rishis) and Brahmanas are the interpretation and commentaries on Mantra/Samhita part of Vedas which helps to explain, understand the meaning and significance of Veda and also provides the way of doing rites (i.e rituals). As it gives Karma Kanda in Vedic Yajna, known as Karma Kanda part of Veda (each Brahamana is associated with one of the 4 Vedas), Since Brahmanas play significant role in Vedas, they are considered as the part of Veda and hence classified as Shruti.
Brahmanas constitutes Aaranyaka at the end and Aaranyaka constitutes Upanishads at the end. In other words, Aaranyaka are extracted from Brahmanas and Upanishads are extracted from Aaranyaka, so, Vedas are generally classified into to:
So four Vedas i.e Rigveda, Samaveda, Yajurveda and Athrvaveda with Samhita, Brahmana, Aaranyaka & Upanishads are Shruti texts means heard not authored, Smriti in most simple word means which is remembered or which is based upon memory, in other words, which is produced out of human intellect or from perishable source, These are texts written/composed by rishi or sages and handed down by tradition, in contrast to Shruti which is divine origin, Smriti is produced out of intellect or by an author. Major Smriti scriptures are: Vedang, Upaveda, Upang, Dharma-Sutra/Shastra and other Sutras, 18 Purans, Itihasa i.e Ramayana, Mahabharata (Bhagavad Gita) etc.,
Commentaries on various Shruti texts by different sages and guru including Brahma Sutra etc. and various scriptures on Darshan Shastra, Hope the above will help you to understand the difference between Shruti and Smiriti along with Vedas, Brahmanas, Samhita, Upanishads, Please feel free to write us at firstname.lastname@example.org, we would be happy to assist you, its all about Sanskars...