The ESSID of a wifi network is its human-friendly name. It usually identifies the network in order to distinguish it from other wifi networks that may be in range, but it's up to the administrator to choose a meaningful and unique name or not.
The BSSID of a wifi network is its machine-friendly name. It is normally unique (but may not be if the wifi provider is malicious).
See Wikipedia and SailorCire's answer for more information.
The UUID mentioned here is not a concept related to wifi networks. It's a concept of Network Manager, the program that you're using. Network Manager assigns a unique machine-friendly name (in the form of a UUID) to each connection. A connection, in this context, is a set of configuration parameters that describe the network (its name, its credentials, etc.). Connections also have human-friendly names; the UUID is used to tell apart connections that have the same human-friendly names.