When using network switches, each port on the switch is its own collision domain.
Since Hubs are Physical-layer devices and do not segment collision domains (which switches do), the answer is "one". Since switch DO segement collision domains, a switch can pass as many frames as it has ports.
data link
VLAN
It operates on the data link layer of the OSI model (level 2). The switch creates a separate collision domain for each port. Although some switches operate on level 3 of the model and are called multi-layer switches.
It is a layer 3 switch
Routers operate at layer 3 of the OSI model while switches operate at layer 2. The data transmission form of a router is called a packet while in a switch, it is called a frame. Routers are mainly used in wide area networks while switches are used in local area networks.
A layer 1 device will extend a collision domain
routing between VLANs
all but IP routing protocols
because one layer is the electrical part, and the other layer is the place where the switch is on.
Switches connect multiple devices on a network, similar to a hub, but with one difference. Switches have the ability to "remember" which device is connected to which switch-port - and only retransmit to switch-port connecting the destination-device for which the data is intended, thereby creating multiple collision domains (which is good - less chance for lost data). In contrast, a hub simply retransmits the data to EVERY interface on it, creating one huge collision domain.
router operates on Layer 3 and can be used as a switch