It stated "multiple devices with network iSOLATION(separated) on a single switch port".
Therefore, its referring to Subinterfaces. Subinterfaces is a virtual interface that divides one physical interface into multiple logical interface.

FHRP stands for First Hop Redundancy Protocol, which is a group of protocols that allow routers or switches to provide backup or failover for the default gateway in a network. FHRP ensures that the network traffic can reach its destination even if the primary gateway fails or becomes unavailable. Some examples of FHRP protocols are HSRP, VRRP, and GLBP.
Reference
1: CompTIA Network+ N10-008 Exam Subnetting Quiz, question 18
2: CompTIA Network+ N10-008 Certification Practice Test, question 9
3: CompTIA Network+ Study Guide: Exam N10-008, 5th Edition, page 263
4: CompTIA Network+ (N10-008) Practice Exam w/PBQ & Solution, question 5
5: What's on the CompTIA Network+ 008 certification? | CompTIA, section 3.1

Explanation
The data link layer is responsible for defining the format of data on the network and providing physical transmission of data. Devices that operate at this layer include switches and network interface cards (NICs).
Encapsulations that are used at this layer include frames, which are units of data that contain a header, payload, and trailer. Frames are used to identify the source and destination of data on the network and to perform error detection. References: CompTIA Network+ N10-008 Certification Study Guide, page 9; The Official CompTIA Network+ Student Guide (Exam N10-008), page 1-6.