Terms you need to understand.
Broadcast: In this case, a Data-Link layer (Layer 2) message sent to ALL devices attached to the same network segment.
Collision: When more then one device transmit data at the same time on shared media, the packets collide, data becomes corrupted and after a random period of time, devices have to re-transmit the data.
Broadcast Domain: All devices that a Broadcast message reaches at the Data -Link layer within a network is called a Broadcast domain. A network can have more then one Broadcast domain and a Broadcast domain is delimited by devices that stop Broadcast messages.
Collision Domain: Anywhere within a network where a Collision can occur. The limits of a Collision domain are marked by those devices that break up Collision Domains.