what is GUID in json payload

Hello Team,

When I get the json payload from the “Equivalent Api” option in Command Center, I see a GUID parameter. What exactly is a GUID, what does it do? In the example below, I can add a VM named vm1 to a VM subclient without a GUID and the backup works.

In this case, is there any harm in using it without a GUID?

{
"content": {
"overwrite": true,
"ruleGroups": [
{
"matchRule": "ALL",
"rules": [
{
"type": "VM_NAME",
"condition": "CONTAINS",
"name": "vm1*"
}
]
}
]
},
"filters": {
"overwrite": false
},
"diskFilters": {
"overwrite": false
}
}