Differences Explained - SNMP

SNMP (Simple Network Management Protocol) is the standard language that your Monro Cloud Proxy uses to "talk" to your hardware to check its health and performance. It allows the proxy to automatically collect data, like how much traffic is on a port or how hot a CPU is, without you having to log into every individual device manually.
For Monro Cloud, it is mostly used when you cannot install the agent (the one your got in your first email). Examples are switches, routers, virtual appliances etc.

Notifications

SNMP v1

SNMPv1 is the original version of the Simple Network Management Protocol. 
In this version, your Zabbix Proxy talks to your device using a Community String, which acts like a simple shared key. The problem is that the Proxy "shouts" this key across your local network in plain text to get data. Since there is no encryption, anyone else on your network can "overhear" that key and use it to access your device information.

SNMP v2

SNMPv2c is the version most people use because it allows the Zabbix Proxy to ask for a "bulk" list of data all at once, making your monitoring much faster. However, it still uses that same shared key system and still "shouts" it across the wire. It's more efficient for your Zabbix performance, but it doesn't solve the problem of people being able to eavesdrop on your network traffic.

SNMP v3

SNMPv3 changes the game by requiring a unique Username and Password that is never sent in plain text. Your Zabbix Proxy and your device use "handshakes" to verify each other and encrypt the entire conversation. Even if a hacker sits on your network and watches the traffic between your Proxy and your device, all they will see is scrambled gibberish.