explain how the Himalayas act as …

The Himalayas act as a boon for India as they act as a barrier to cold siberian winds. They give tropical touch to the climate of India. They stop rear-bearing monsoon winds from crossing into Tibet and force the wids to shed their moisture within Indian- subcontinent.

They block the rain bearing monsoon winds from the Arabian sea and the bay of Bengal. Therefore, the North Indian plains receive plenty of rainfall.
There is a lot of snowfall in the higher regions of the mountains. The snow melts in summer. The rivers like the Ganga and Brahmaputra which rise among these ranges are fed by the waters of the melting snow. These rivers never dry up in the hot summer months.
They protect India from the cold, biting winds blowing from North Asia. So, the winters of North India are milder than those beyond the mountains.
These mountains with their high peaks and deep ravines are difficult to cross. Therefore, they prevented many invaders from easily invading our country. Thus, the role of Himalayas as a guard of our Northern boundary is very important.
The Himalayan rivers bring rich silt from the mountains and deposit in the plains below. This silt has made the northern plains very fertile.
There are thick forests on the Himalayas. They supply us with valuable timber, medicinal herbs, honey and wax etc. They also provide a home to innumerable birds and animals.