Is WoW paid monthly?

Could you please clarify for me whether the popular online game World of Warcraft, or WoW for short, requires a monthly subscription fee in order to play? I've heard conflicting information about whether it's a free-to-play game or if there's a recurring cost associated with maintaining an active account. I'm interested in trying it out but want to make sure I understand the financial commitment upfront. Thank you for your assistance in clearing up this matter.