Foremost, Rudra and Shiva are one and the same.
According to Shiva Purana, there is a story about the connection between Rudra and Shiva.
One day Lord Brahma asked Shiva to create some living beings, as he was getting bored by creating ordinary mortals.
Then, Shiva created few immortal beings called as Rudras. They were totally Eleven, namely
- Kapali.
- Pingala
- Bhima
- Virupaksha
- Vilohita
- Ajesha
- Shasana
- Shasta
- Shambu
- Chanda and
- Dhruva
So, they were together referred as 11 Rudras.
Being the head of these immortal beings, Shiva is addressed as Rudra.
The hymns of Rig-Veda have lot of references to Shiva in the name of Rudra. They all portray Shiva as the highest God, a mighty archer, the most terrible form of God, the fire God and so on, these all express the fiery aspect of Shiva .
Shiva is the benign aspect of Shiva, where as the contrast Rudra is the fierce aspect of Shiva, thus bring the contrasting features of Shiva.
The literal meaning of Rudra is, “Roaring Storm / fire / fiery red”.
The term Rudra focuses the fiery aspect of Shiva, which is destruction.
One para from Rudrashtakam ::
- Prachannddam Prakrssttam Pragalbham Paresham
- Akhannddam Ajam bhaanu_Koti Prakasham
- Tryah_Shoola Nirmoolanam Shoola paannim
- Bhajeham Bhavaani _ patim ,Bhaava_gamyam
- Meaning is :: I bow to You Rudra , who is terrible, eminent and extremely strong, who is the highest and greatest God.
- Who is ever Unborn and whole, and has the brightness of million Sun’s.
- Who has a trident in His hand, the three spikes of which uproots the bondages of the three gunas namely Tamas, Rajas and Sattva.
- I bow to you, the Husband of Devi Bhavani, who can be attained by devotion.
Source:: Shiva Purana pravachanam by Chaganti Garu.