This is the 216th most frequent Russian word.
многих
"Многих" means "many" (genitive or accusative plural form) in English.
Here, 'многими' is the instrumental plural form of 'много', used with 'друзьями' to indicate whom the subject met with or among.
Я познакомился с многими новыми друзьями на этой конференции.
I met many new friends at this conference.
In this example, 'многих' is the genitive plural form modifying 'экспертов,' indicating that it relates to a large but unspecified group of experts.
Он доверяет мнению многих экспертов.
He trusts the opinions of many experts.
In this sentence, 'многих' is the genitive plural form of 'много', used to describe 'людей,' indicating that it refers to a large and indefinite number of people.