Single Rate tariffs
Single rate is the simplest electricity tariff, and is still the most common tariff used across Australia.
Single rate means that the price you'll be charged per kWh of usage will not change by the time of day or by the day of the week that you use that energy.
Single rate is the simplest tariff type, because it does not require time of use to be recorded alongside the consumption, so it's used with older 'accumulation' meters which  are able to record only your aggregate kWh consumption.
Single rate is the most common tariff type in Australia, and is supported by even the oldest meters.
Flat single rate tariffs
The simplest tariff of all is the flat single rate tariff where you'll be charged the same rate per kWh of usage no matter when you consumed the energy, and no matter how much you consumed over the billing period.
Stepped single rate tariffs
So called 'single rate' tariffs may not literally be single rate.
Some single rate tariffs are actually 'stepped rate', or 'block rate' which means you'll pay a different price per kWh once you've crossed a threshold of total consumption for the billing period.