Services in Linux are generally things that run in the background providing a useful function or 'service'. Systemctl is the 'service manager'.
systemctl is the service controller interface in Linux. It is the brains of the operation. Using this program you can start, stop, disable or tell a service to run on startup automatically. These functions are generally what most use cases of systemctl fall under.
To temporarily enable or disable a service (resets on boot)
sudo systemctl stop <service_name>
sudo systemctl start <service_name>
To permantly enable or disable a service (does not resets on boot)
sudo systemctl disable <service_name>
sudo systemctl enable <service_name>
The snap store manages services for applications installed with snap internally. You can manipulate services managed by snap using the following
sudo snap services
sudo snap restart <service_name>
sudo snap start/stop <service_name>