If you are a devotee of Lord Shiva, then knowing about the eight forms of Shiva is very important.
They are called the Ashtamurthys.

The concept of Ashtamurthys explains why we say that this universe is a manifestation of Shiva.
The five elements, the panchabhutas that the universe in made up of are all Shiva.
Bhumi, Jalam, Agni, Vayu, and Akasha are all Lord Shiva.
Whenever you see anything that is solid, you should know that it is Shiva.
Whenever you see anything that is liquid, you should know that it is Shiva.
Whenever you see anything that is gaseous, you should know that it is Shiva.
Whenever you see any form of energy like fire, lightning, wind, you should know that it is Shiva.
Whenever you see any empty space, you should know that it is Shiva.

So the material universe is nothing but Shiva.

Surya and Chandra, they are two visible Gods.
They are also Shiva.

Whenever you see someone who is worshiping, then you should know that he is Shiva.
The worshiper is called Yajamana.
So the eight forms of Shiva are - Bhumi, Jalam, Agni, Vayu, Akasha, Yajamana, Surya, and Chandra.

You can offer Namaskaras to the Ashtamurthys -
ॐ शर्वाय क्षितिमूर्तये नमः
ॐ भवाय जलमूर्तये नमः
ॐ रुद्राय अग्निमूर्तये नमः
ॐ उग्राय वायुमूर्तये नमः
ॐ भीमाय आकाशमूर्तये नमः
ॐ पशुपतये यजमानमूर्तये नमः
ॐ महादेवाय सोममूर्तये नमः
ॐ ईशानाय सूर्यमूर्तये नमः

There are also temples dedicated to the Ashtamurthys.
Every Surya temple is of Ishana, the Suryamurthy.
The Somnath temple of Gujarat and Chandranath temple of Bengal are of Mahadeva, the Chandrsmurthy.
Pashupatinath temple of Nepal is of Yajamanamurthy.
Ekamreswara temple of Kanchipuram is Sharva, the Kshitimurthy.
Jambukeswar temple of Tiruvanaikaval is of Bhava, the Jalamurthy.
Arunachaleswara temple is of Rudra, the Agnimurthy.
Sri Kalahasti is of Ugra, the Vayumurthy.
Chidambaram Nataraja temple is of Bhima, the Akashamurthy.

You should try to visit these temple at least once in a lifetime.