This is the 567th most frequent Italian word.
politici
"Politici" means "politicians" in English.
In this sentence, 'politici' is used as a noun to mean 'politicians', referring to individuals involved in politics.
I politici stanno discutendo una nuova legge.
The politicians are discussing a new law.
Here, 'politiche' is used as an adjective (feminine plural) relating to 'decisions', derived from 'politico', which connects to political matters.
Le decisioni politiche influenzano tutti noi.
Political decisions affect all of us.
In this context, 'politiche' is again an adjective (feminine plural), but it modifies 'opinions', indicating their connection or relevance to politics.