Core (Server) Switch- Switch(s) dedicated to facilitating fast and redundant communications between physical/Virtual Servers, firewall's and other core equipment. These switches are generally uplinked to separate distribution switches via 1G aggregate or 10/40G links or are stacked into separate distribution switches (requires all switches to be the same series)

Distribution Switch- Switch(s) dedicated to the distribution of LAN connectivity to one or more areas of a building. Usually where your PC's, AP's, Camera's, printers, phones, etc. are plugged in. These switches are generally uplinked to the core switches with redundant (1g aggregate), high-speed(10-40G) uplinks or are stacked into the core using the available stacking method (requires all switches to be part of the same series)

Switch Stack- Specifically refers to two or more switches which are connected together using a formal stacking method and work together as one, logical switch. This allows for aggregated links to span between physical switches in order to provide greater bandwidth to uplinked servers and switches as well as to provide switch connectivity redundancy. You can manage a switch stack from a single IP address and can generally expand the stack by adding in more switches of the same series. Stacking is NOT uplinking.

Uplinking- An uplink is simply a standard ethernet connection to another ethernet device that stands in line between the device and it's default gateway. This facilitates ethernet connectivity between devices, but does not allow for stacking between devices. Uplinks can be a single ethernet connection or can be Aggregated between devices for more speed and link redundancy. Aggregated links connected to a switch stack can span multiple physical switches in the stack to provide physical switch redundancy as well.

Downlink - A Downlink is very similar to an uplink however it is going in the reverse direction; away from the devices default gateway.