What is the importance of subsidization and where can it be utilized best?

Good question, as usual!

Subsidization is very important. I’ll assume you’re referring to Government subsidization?

Government subsidization generally aims to keep the price of certain goods, services & products artificially low, thereby enabling average income citizens to afford buying (and benefitting from) them. This can have positive impact on the overall well-being & purchase power of a population, thereby boosting economies in times of hardships. 

It may also have negative negative effects, though, that include increasing  the deficit spending of government & creating controversies as to better channeling of such subsidies towards standard heavy-cost high-demand posts like: infra-structure, education &  health care.