What does 1 or 2 tons mean when talking about air conditioners?

Tons are a unit of measurement. The text books put it like this.
Ton of refrigeration (cooling): Refrigeration effect equal to the melting of 1 ton of ice in 24 hours. This may be expressed as follows: 288,000 Btu in 24 hours, 12,000 Btu in 1 / hour or 200 Btu / min. The standard phrase is the 1 ton of cooling or 12,000 Btu’s per hour. What is a BTU? British Thermal Unit (Btu) quantity of heat required to raise temperature of one pound of water one degree Fahrenheit.
So back the original question, what does 1 ton mean to me when buying an air conditioner? The phrase 1 Ton unit or (12,000 Btu per hour) means that it will cool a standard insulated room that’s 450 to 550 square feet. (Sq ft rule from Energy Star.gov). But this is only a rule of thumb, a standard room with 2 people.
Remember that if you live in the Nevada or Minnesota the rule of thumb is going to have Btu’s added or subtracted.