Telepath grants Mandalay the ability to communicate with anyone through thought. She can instruct and send messages to multiple people at once. The range of her abilities is unknown, but it was enough to reach everyone inside The Beast's Forest at once. Telepath is only one-way communication, so its user cannot hear their targets' thoughts or receive responses.
When Mandalay is fighting against an enemy, she can use her telepathy to send messages directly to her foe's mind with the intention of distracting them. This throws them off, causing them to lower their guard against Mandalay’s next attack.
- Telepathy: Wikipedia article on the concept behind Shino's Quirk.