This is the 11444th most frequent Russian word.
доверительные
"Доверительные" means "confidential" or "trustful."
The word 'доверительные' is used to describe the nature of the relationship as based on trust, showing its role as an attributive adjective.
У нас с ним доверительные отношения.
We have a trusting relationship.
Here, 'доверительные' characterizes the advices as trustworthy and possibly private, implying the adviser's integrity.
Она всегда даёт доверительные советы.
She always gives confidential advice.
In this sentence, 'доверительных' modifies 'беседах' to reflect the level of openness and mutual trust during the discussions.